texts:
Here in this circuit,
We have the load connected to a diac and triac circuit along with a variable resistance and a capacitor.

When the circuit operation begins initially, the energy is stored in the capacitor until it reached the required threshold value to activate the diac ( D1). Once that happens, the diac ( which acts as the voltage regulator) generates the required gate voltage to activate the triac which is the main component contributing to the voltage regulation across the load.

The variable rheostat is the pointer regulator under manual control. By adjusting the rheotstat, we can control the charge in the capacitor which can further control the voltage drop across the load.
And this regulation in voltage finally leads to change in the brightness of the bulb.
Hence, when not doing any heavy activity like reading or writing, the bulb or tube light dimness can be attained and hence can lead to less power consumption.
Also, if we use a purely resistive circuit for this purpose ( using a variable resistance or rheostat), the ohmic resistance of the circuit increases. Hence, using triac and diac switching devices help in reducing the ohmic losses and increase the efficiency of the circuit.

I wanted to know how efficient this concept would be in power saving. Will it contribute to a substantial level in reduction of power consumption if applied to an entire house?

Link to the circuit: http://www.eleccircuit.com/wp-content/uploads/2010/09/light-ac-dimmer-120watt.jpg


texts: Is there any pitfall to using resistors in series AND parallel for an LED array?

texts:
I've seen a lot on LEDs and series vs parallel resistor usage, but found nothing regarding the combination of both, so here goes.

I am working on a watch of sorts, that will work similar to a 7-segment display, where different LEDs are lit simultaneously depending on the driver's output (sometimes 2, sometimes all 7), so I will use that as an example.

In order to conserve battery, I am looking to have a low brightness during "normal" operation, with a momentary high brightness option. Since this needs to be rather small to be wearable I am, of course, looking to minimize component count. Cost is relevant, but much less of a factor than attaining a small size that can be hand soldered.

It is widely understood that running parallel LEDs on a single resistor is not the best approach, and I have allowed for a resistor-per-LED arrangement in my design, but I would like to be able to bypass SOME of the resistance temporarily.

What I figured I could do is put the Resistor-LED series pairs in a parallel array that feeds to a single resistor with a bypass, as in this schematic:

simulate this circuit – Schematic created using CircuitLab

So, the question: Would placing a single resistor in series with a parallel LED array be as bad if the LEDs also had dedicated series resistors, and if so, are there other alternatives for the dim/bright outcome I am looking for?

Additional Info
- I am planning on a 3v (2xAAA) battery source running LEDs with a Vf of 2-2.2.
- Once I have my LEDs, I intend on testing different resistance values for brightness yield, but am hoping for around 2-4 and 7-10 mA for the low & high respectively.
- The actual array will have 12 LEDs, with a maximum of 9 lit at one time.
- There will be 4 "digit" arrays in total.
- I am comfortable working with SOIC and 0805 (and some 0603) packages.
- If there is a risk of (slightly) uneven brightness from one LED to the next, that will be ok, as it will give a "battle worn" look that will work with the design.


texts:
Somebody can send mee the datasheet of RCA 37428 transistor.
Thank you!


texts:
This device is installed in our electrical panel which act as a timer to control the on/off operation for our LED billboard outside my office. I searched around the device for the brand and model it did not state anything or probably written in chinese character which I am not familiar. The previous electrical engineer already left without leaving his technician any clue on how to operate this device.

Now I need to reprogram it to switch on the billboard at a different time. it has one serial cable that can be connected to a laptop and the technician told me the previous engineer used to plug it to his laptop and run a program called "MK Power" to program the timer. I guess that software came with the device since the tech described a window based program with specifics fields to set time and delay.

Anybody recognize the device and know where I could find the software for it?


texts: I need to read a .mif file created by IP Core Gen in xilinx

texts:
Here is my code:

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
use STD.TEXTIO.ALL;

entity new1 IS

    port(data : IN STD_LOGIC_VECTOR(7 DOWNTO 0));
end new1;

architecture Behavioral of new1 is

begin
    process

    type my_file IS FILE OF INTEGER;
    file data_in : my_file;
    variable fstatus : file_open_status;
    file_open(data_in, "c:\temp2.mif", read);

end process;

end Behavioral;

The code is giving error:

  "unexpected identifier"

in the command file_open.


texts: Soldering basic mini LED dual flasher kit from instructions

texts:
I need help how to make this flasher work. I am fairly new to soldering and circuitry. This is the image.

all parts:

just the circuit board:

I tried doing it without soldering, is this right?

This is the only assembly instructions they gave us.


texts: BJT - Influence of increasing \$V_CE\$ on \$I_c\$

texts:
I struggle to understand to relationship of Ic and Vce.
I have the following circuit: A voltage supply at 12.4V, a LED with 0.2A current 9V, a BJT with the Ic-Vce relation shown in the picture below and a resistor to ground.

As far is I understood and measured, the LED can be considered a constant current source.

The strange behavior I do not understand is the following:
If i increase the supply voltage by 1V to 13.4V, the LED's voltage remains the same, so does the voltage over the resistor. Thus the current mus still be the same, 0.2A.
I measured an increase by 1V over the transistor, jumping from 1.4 to 2.4.
If i now examine the Ic - Vce graph, I cannot understand why the current doesn't change.

I would be really glad, if someone could enlighten me.


texts: How can we detect the source of the radio emission?

texts: if someone is generating frequency, can receiver detect from where exactly it's emitting? If someone is emitting on illegal frequency band, how it can be caught?


texts: Is it possible to power target microcontroller from AVRISP mkII using Atmel Studio

texts: I'm using the Atmel Studio IDE and a AVRISP mkII to program microcontrollers. I've always powered the microcontrollers to be programmed with an external power supply but I was wondering if it is possible to power the target microcontroller through the AVRISP mkII itself?


texts: Touching certain pins (grounding body capacitance) causing pcb to work

texts:
I'm using a siren generator circuit to generate signal and trace it using an amplification circuit.

This circuit is working and tested before but this time I'm not getting good sound on the amplifier unless I touch pin number 3 or 7 of IC2 (555).

I know my body has capacitance and resistance (wiki says 100 pF and 1.5 kOhm) which explains why in such cases people ground a 100 pF cap.

Yet that didn't solve my problem, an open circuit of 1000 uF seemed to boost the output a lot but not quite as much as my physical touch to the pin does.

Also it's the same problem across 5 boards, so I doubt it's soldering problem

Here is the schematic:

Here is the schematic for the 555:


texts: What does 232 signify in the RS232 standard?

texts: "RS" in communication standards RS232 and RS485 stands for "Recommended Standard". But what information does "232" or "422" or "485" convey in the name? What naming convention is used for numbers succeeding the letters "RS" when naming the RS standards?


texts:
First of all I have to admit that this is a homework question.

Screenshot of it is given below,

I am able to find only two things, and they are given below :

Magnetic force acting on each frame is towards the right hand
direction.
E.M.F is induced due to the changing magnetic flux .

So how can I come out of this question?


texts: Initial permeability of toroids in ATX power supply?

texts:
I'm interested in re-using output side or possibly the line filter toroids from a junk ATX switching supply. All turns are removed, just the core.

I think these are powdered iron cores and any guess what the initial permeability may be for these cores?  My application is in the low end of HF region (1 to 7 MHz) to be used as transmission line transformer cores.


texts:
I'm studying the attached circuits made up from a RLC network (with a Crystal) and an operational amplifier.
I've never used crystal with OPA. How does this OPA configuration work?


texts:
How could i determine a transfer function (A(s)) which responds to a symmetrical 1Vp-p 1kHz square-wave input signal, and gives a 5Vp-p square-wave output signal

with tilt==> δ=10% and rise/fall time ==>tr=tf=10μs


texts: Polarity symbols on universal AC-DC adaptor

texts:
I have a universal AC-DC adaptor that has the following symbol by the polarity switch:

Is it safe to assume that the top part of the diagram indicates the polarity of the inner surface of the cylinder, and the bottom part indicates the polarity of the outer surface?

I'd like to know which way I should push the switch to match the required positive polarity on my 12V DC device:


texts: TV antenna problem: Transmission line problem

texts:
I have to solve the following problem:
A TV antenna lead-in wire 10cm long has a characteristic impedance of 250 \$\Omega\$
and is open-circuited at its end. If the line operates at 400 MHz, determine it's input impedance.

I came up with a solution to this problem, but I'm not sure it's right. I have some doubts. I don't think I'm using the right equation for \$Z_{in}\$ I don't know how to pick if I should use the lossy or lossless \$Z_{in}\$ equation.

Lossless Case: \$Z_{in}\$ \$=\$ \$Z_o\frac{Z_L + jZ_o\tan(\beta L)}{Z_o + jZ_L\tan(\beta L)}\$

Lossy Case: \$Z_{in}\$ \$=\$ \$Z_o\frac{Z_L + Z_o\tanh(\gamma L)}{Z_o + Z_L\tanh(\gamma L)}\$

My Solution:

Since we are given that the it's open circuited choosing the lossless case we get the following simplification because \$Z_L =\infty \$

\$ Z_{oc} = \frac{Z_o}{jtan(\beta L)}\$

So we need to calculate \$\beta\$ This could be calculated by using the following formula:

\$\beta = \frac{\omega}{u}\$

We know \$\omega = 2\pi f = 2\pi(400*10^6)\$ and with that we can find the speed assuming air is free space so therefore u = c, where c is the speed of light.

\$\therefore \beta = \frac{2\pi(400*10^6)}{c} = \frac{8\pi}{3}\$

\$ Z_{oc} = \frac{Z_o}{jtan(\frac{8\pi}{3} 0.10)} \approx -j225.10\$

Does this answer make sense? This is my first time dealing with Transmission Line Equations, so I'm not so sure.


texts: Why should care be taken while closing a capacitive circuit?

texts:
The other day in class, our professor told us that care should be taken while closing a capacitive circuit and while opening an inductive circuit.

Why is this so?

I partly understand the inductive part. Since inductor only allows current to change gradually through it, if the current flow is suddenly stopped, then the voltage through it would suddenly increase, damaging it.

I'm unable to think of something for a capacitor.


texts: what is the difference between ISE and Vivado?

texts:
I am xilinx ISE and virtex 5 engineer.

I found Vivado something when I ran across the internet.
What is the difference between ISE and Vivado?

Should I have to move to Vivado from ISE?


texts: SPI communication not working during Run time?

texts:
For my project i need to communicate between Microcontroller C8051f350 Datasheet (Silab Microcontroller) and TI DAC116s997 DataSheet IC through SPI.

The problem i am facing a problem in SPI communication. SPI communication works fine when debbugging (single step). But when i run programme without break points SPI communication fails.

Here is Code for communication,
SPI Initialisation

//! @brief Initialise the SPI
// SPI mode - 0, CPOL=0 CPHA=0
// SPI0CN = 1, ENABLE SPI
// fSCK =SYSCLK/2*(SPI0CKR+1)
// SYSCLK = 24.5Mhz SPI0CKR = 9, SPI FRQ(fSCK) = 1.2Mhz
#define Init_SPI()  {                                               \
    SPI0CFG   = 0x40;                                                   \
    SPI0CN    = 0x01;                                                   \
    SPI0CKR   = 9;                                                  \
}

Initialisation process for DAC

MT_SPI_Write(8, 0xC33C);        // RESET the DAC
MT_SPI_Write(2, 0);             // Followed by NOP command after reset

Continously write DAC value in 1ms Timer ISR

/**
 * @brief   1ms Timer ISR for timer 3
 * @author  Sushant
 * @param   None
 * @return  None.
 */
void ISR_Timer3()   interrupt 14
{
    Word lwRes;
    CLEAR_TIMER3_FLAG();
                //  DACCODE ADDRESS, DAC VALUE
    lwRes = MT_SPI_Write(4,          32767);
    MT_SPI_Write(0x89, 0);      // read status register

}

SPI Functions:

/**
 * @brief   This function writes 24 bits on DAC through SPI
 * @param   lbAdd - Address of DAC register
 * @param   lwData - Data to be written at address specified
 * @return  16 bit data received from DAC in return
 */
Word MT_SPI_Write(Byte lbAdd, Word lwData)
{
    UN_Word lunResult;
    UN_Word lunData;
    lunData.W = lwData;
    DAC_CS = 0;                                 // CS = 0
    Send_SPI(lbAdd);                            // Address of register
    lunResult.B[0] = Send_SPI(lunData.B[0]);    // Higher byte of register
    lunResult.B[1] = Send_SPI(lunData.B[1]);    // Lower byte of register
    DAC_CS = 1;                                 // CS = 1

    return lunResult.W;
}
Byte Send_SPI(Byte lbData)
{

    while(!TXBMT);          // Wait if transmit buffer is not empty

    SPI0DAT = lbData;       // Write the data in SPI Tx buffer

    while(!SPIF);           // Wait till transfer is complete

    SPIF=0;                 // Clear the transfer complete flag

    lbData = SPI0DAT;       // read the data from SPI Rx buffer

    return (lbData);        // Returns the data
 }


texts:
I'm trying to regulate 12V to 4.7V with a zener diode. (I'm doing this to protect an AVR's gpio pin, so the current is very low.) I tried the simplest circuit with the zener, but it does not work as expected.

simulate this circuit – Schematic created using CircuitLab

I expect the multimeter to measure 4.7 Volts on the zener diode, but it only shows about 3.2-3.3 Volts. I replaced the diode with other ones with the same model, and the results are the same.

Are my diodes faulty, or am I doing something (very) wrong?


texts: Active guard shielding for instrumentation amplifier

texts:
I want to use the the AD8221 amplifier as a conditioner for my load cell. I saw that to reduce noise I can use an "active guard shield driver" between the "REF" of my amplifier and the shield.

If someone has already worked with something similar or have knowledge on this subject it will help me if you can explain me why and how it is working? And if I really need to use it?
Is it not enough to just connect the "ref" to my GND and the same for my shield?


texts:
I am trying to work with a Microchip MCP2515 CAN Controller (16 MHz oscillator) alongside a MCP2551/61 CAN transceiver. I have been successful trying to setup the device via SPI, but I am unable to send/receive CAN frames (trying to send throws a large count of error frames, increasing the register error counter and making the interface go error-passive and bus-off).

I suspect the reason of these errors is the bit-timing although I am not so sure about it.

Does the CAN bit timing for each device affect only receiving, or both receiving and transmitting?

In this case, does the sampling point, phase segment 1 and phase segment 2 affect during sending?

Update: I just figured out why the controller was not working... The MCP2551 transceiver was dead... I replaced it, and it worked all of a sudden.


texts: Help Identifying a component for PCB repair

texts:
I'm helping a friend by attempting to repair this display PCB.  It uses 24vac input and he accidentally hooked it up to 120vac.

I am trying to identify the two components in this picture under the burn marks.  I'm pretty sure they are diodes but am looking for more specifics so that I can order replacements.  Anyone able to direct me anywhere or know anything about the two components labeled MX 21A.


texts:
I'm looking for some kind of idea for controlled load for AC source testing. The output signal of source is a bipolar sine wave 5 Vpk (so it varies from -5V to 5V) and it has 1.5kOhm series resistance.

My goal is to make a variable load, so the output voltage will be reduced to around 30% of nominal (unloaded) voltage value. That means that i need to figure out how to make a controlled resistance with values down to 750 Ohm. Or make some kind of variable load current source.

Reducing of signal should be smooth in all range or with possible small steps (not just on/off variable load) and sine can't be distorted. Microcontroller will be used for controlling.

The obvious solution is digital potentiometer, but these for bipolar signals (basically with ex. +-15V voltage supply) are not very common.

I will be grateful for any solution ideas for this problem. Thanks.


texts: Would be possible open a electronic lock, like that used in door, through induction using an EMP device?


texts: Do Electronic Engineers need to be "licensed"

texts: Do Electronic/Electrical engineers need to be licensed? I have heard something along these lines but I do not recall where. And if so what is the license name? If I take a stab at my own question I am assuming it might have to do with specific engineers, like if you're going to work on power systems for a power plant or something??? What about an embedded Systems Engineer?


texts: Battery level on battery indicator drops when i connect a load?

texts:
I've got this cheap battery level indicator that has 4 battery level segments, it is connected to a 12V-18AH lead acid battery that I to charge my laptop and my 1W light bulb.

I really can't seem to understand the behavior of it, as soon as I plug the charger to charge the battery it goes full (4 segments on) instantly, then goes back to original state as soon as I remove it.
And when I start charging my laptop, it always drops a segment, then goes back as soon as i remove it as well.
I feel it's more of a load indicator?!

I would appreciate an explanation for this please.
 Sorry for my english.


texts: Approximate weight ratio between 50/60 Hz and 400 Hz electric machines

texts: I need a fast (not to much elaborated) approximation figure of how lighter will be a transformer or motor designed to run on 400 Hz compared with an equivalent machine with the same power capacity designed to run on 50/60 Hz.


texts: Stellaris LM4F120 Series: What happened to it?

texts:
A while ago I got a Stellaris Launchpad for the new LM4F120 MCU but did not get around to trying it out.

When I now tried accessing any information on the LM4F120 series at TI, anything related to it seems to have disappeared and old links are redirected to the TM4C123 series. I can not even find any datasheets.

What happened? What are the differences to the TM4C123 series? At first glance there does not seem to be any difference.


texts: MSP430 multiple slaves in SPI communication

texts:
I want to make an MSP430G2553 communicate using SPI with a 7-segment display and with another microcontroller MSP430G2452.

So the MSP430G2553 would be the master and both the 7-segment display and MSP430G2452 would be slaves. The master will acquire a measurement from the slave microcontroller MSP430G2452 and then display it on the 7-segment display once per second.

I have been led to believe that it is not possible to connect the two slaves on the same SPI bus. Is this the case and if so why not?


texts: How to determine phase angle of a three-phase circuit

texts:
I am experiencing difficulties with a question:

  A balanced three-phase load shown in the diagram is connected across a 380V, 50 Hz three-phase supply, ABC phase sequence. The voltage VAB is taken as reference.

Part of the question I am trying to answer includes converting the WYE circuit to a Delta circuit as I have done:

Now, my main question is how do I work out the phase angle of each component?
My textbook does not have notes on how to determine the phase angle. All they say is VBC is generally used as the reference phasor. But in this case, VAB is used as the reference phasor and I don't know how to determine the angles for the phasor diagram. I thought of rotating the reference diagram of VBC so that VAB = 0, VAC = 120 and VBC = 240. Would I be correct on this approach? Please advise


texts: Communications problem between esp32 and AD5763

texts:
I am trying to make huzzah32 (ESP32) communicate with AD5763 but I am having some problems with writing and reading in registers.
I am sure that the bit sequences I send are actually the ones I wanted (I checked them with the oscilloscope).
What I'm trying to do is reading and writing of a register.
To do this I send these three commands in sequence:
// writing
00010001 00001111 00001111
// reading
10010001 00000000 00000000
// nop
00000000 00000000 00000000

In response to the nop, I would expect to receive the values that I wrote in the director, so something like this:
10010001 00001111 00001111

but instead I always get a copy of the read command:
 10010001 00000000 0000000000

I tried to read several registers and each time it returns the copy of the command.
By setting the SDO-Disable command I actually see that the DAC does not respond to me or not, depending on the disabling\enabling.
To be more precise and complete the setup information, I use this PINs configuration:

sync-negate: LOW during the communication, HIGH otherwise
clr-negate: HIGH
ldac-negate: LOW
rstin-negate: HIGH
miso / mosi: for the communications

Anyone have any idea what it could be?
SUPPLEMENTARY INFORMATION

The code I'm using: https://github.com/XaBerr/AD5763-firmware
Huzzah32 datasheet: https://cdn-learn.adafruit.com/downloads/pdf/adafruit-huzzah32-esp32-feather.pdf
AD5763 datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/AD5763.pdf


texts: Voltage at soldering iron tip, should I be worried?

texts:
I discovered that my soldering iron has voltage at the tip and it seems to increase the hotter the iron gets. Should I be worried? I've been trying to repair an old CRT monitor and I'm worried the issues I've been having are due to this cheap iron damaging something.

How to meassure voltage of an soldering iron tip? Where to put probes?


texts: variable 555 circuit with equal LOW&HIGH frequency

texts:
I've started to play with the 555 chip. There is a lot of documentation out there. So I want to create a strobe light project, with an adjustable frequency.

I've played with a lot of capacitors (1nf, 1uf, 10uf, 100uf, 1000uf) and resistances (330ohm, 1kohm, 10kohm, 100kohm, 1mohm). If I can change the frequency, I run into the problem where the light does not stay off for an equal amount of time than it stays on.

For example, right now I have this kind of output when I play with my potentiometer (numbers are not accurate):

100ms on, 100ms off
500ms on, 100ms off
1000ms on, 100ms off

But I'm trying to achieve this kind of scale:

100ms on, 100ms off
500ms on, 500ms off
1000ms on, 1000ms off

I have multiple 555 chips, but I can't find a way to have the on and off signal to have an equal duration.


texts: Difference between RMS and PMPO in radio speakers

texts:
The radio speakers come with their loudness unit either in RMS or PMPO watt.
What is the difference between the RMS and PMPO in sound system?


texts: Decomposing a waveform in LTspice to view only the transient component

texts:
In electric-circuit theory due to superposition for an LTI system, the voltage can be thought such that it is sum of of a transient response plus a steady state response.

For example below the voltage waveform's steady state response is a sine and the transient response is an increase with negative exponential.

The above is an example. Is it possible to view only the transient response of such waveform in LTspice by not using a complicated circuitry? What came to my mind something like a peak detector but I don't know how I can accurately implement it by a behavioral source ect.


texts: PWM switching in BLDC motors: ratio between switching losses versus conductive

texts:
There were some good posts regarding choosing the PWM switching frequencies considering the needs of the motor control. Here I am focusing rather on understanding of how to decrease losses in the power bridges of the controller. Mainly analyzing two main components of these losses: the conductive losses (power MOSFETS + inductor + resistive load)  versus switching losses in power MOSFETs (Miller effect between full open and fully closed state).

Consider example of 3000RPM motor , 50Hz outer loop frequency, having 4 pairs of poles whence 200Hz outer loop motor frequency. According to the accepted "rule of thumb" the required PWM switch frequency starts from 10 x 200Hz = 2kHz
This number is thought of been able recreating the "natural sinusoidal" EMF of the motor coils needed for voltage control of the coils current.

Let's assume that I have other means to change the voltage applied to the half bridges MOSFETs in order to control the speed of the motor (in this case to maintain steady 3000RPM). Is it correct to assume that I can reduce switching losses in the power inverter if I just apply the same switching frequency 2kHz thus not recreating sinusoidal waveform at all but only switching polarity of motor phases to make motor run with constant speed ? (Again, assume for a moment that issues of the close loop, position sensing and fine tuning are passed to another block - the voltage controller , adjusted for a permanent speed.)
Or are the conductive losses increase so dramatically that saving on switching losses will not help at all?
What kind of losses prevail within say 100Hz to 10kHz switching range ? Would conductive losses increase dramatically in the lower end of this range so that eliminating switching losses don't matter ? Or is it more beneficial to use upper end of the range to have minimal total losses?

Yet one more way to put this question: Is PWM switching frequency chosen only to recreate sinusoidal voltage control of the motor or is it also helping to decrease overall energy losses in the inverter compared to the long period of the ON state conductive losses in the MOSFETs?

Anybody who had heavy practical experience with motor control please share your thoughts. JonRB please?
Edit: To clarify the expression "to recreate sinusoidal voltage control" is only one purpose of using PWM, another one - more frequently used for - is to control voltage level below of the provided fixed voltage source. In any case, this post is not about voltage control but about power losses in the inverter : the balance between conductive losses vs switching losses.


texts: How can I go about making temporary test connections in pcb while prototyping without soldering?

texts:
I recently ordered some PCB bits from Adafruit to assemble a widget. I want to make temporary connections between different PCBs, but am not convinced I want to solder and then desolder and resolder wires while I am testing and prototyping.

My initial thought was that there might be some sort of cone-like connector I could shove through the pads that would make temporary contact, but can't seem to find anything.

Is there a solution to this problem? I could use the headers that came with the PCBs but then I'd have to desolder those or buy new PCBs once I had the wiring diagram figured out, which is something I'm also not keen on doing.


texts: I'm not sure how I go about finding \$V_0\$ in this circuit. The current source just confuses things for me. \$R_1\$ = 10 kOhms and \$I_g\$ = 17 mA in this example.


texts: Power measurement on neutral instead of line

texts:
what is the advantage or disadvantage of measuring the power on neutral insted of line in a single phase wiring. Generally I have observed that metering chip is given input from line to its Vin or Iin. But some designs use neutral metering instead of line metering. What is the pros/cons of using neutral metering?
Regards,
Shreyas.


texts: 3.3v to 5v conversion with non-5v tolerant part. (single npn transistor?)

texts:
I was wondering if I can convert 3.3v to 5v when the 3.3v part isn't 5v tolerant.

I was thinking of using this layout:

However I'm not sure if the gpio pin will get 5v "for a second" or if this is safe? Additionally, I'm not sure how to work out if 1MHz or 10MHz is possible here.

Would it be better to use a pnp transistor instead (SS8050?) so that the gpio could trigger the base directly?

If this is the wrong way to do this, is there a cheap unidirectional 3.3v to 5v converter IC which ideally has a schematic in Eagle?

EDIT: To clarify. I'm hoping to use the 5v to communicate with a shift register (which needs around 3.7v input minimum). Not to power the shift register.


texts:
My question is about using FRC as an oscillator source and OSC2 pin as an I/O pin.

In several different manuals on dsPIC30F chips (ex: DS70139G, page 126) it is written:

   LP     Secondary       0 0 0   XXXXX  (Note 1, 2)
   FRC    Internal FRC    0 0 1   XXXXX  (Note 1, 2)
   LPRC   Internal LPRC   0 1 0   XXXXX  (Note 1, 2)

   Note 1: The OSC2 pin is either usable as a general purpose I/O pin or is completely
   unusable, depending on the Primary Oscillator mode selection (FPR<4:0>).

I carefully searched manuals, errata, forums, etc. But I cannot find clarification on how to set the FPR bits in the FOSC register to be able to use OSC2 as an I/O that the Note 1 suggests. Is this possible at all?

Errata on dsPIC30F3012 suggests using FRC with PLL and postscaler to make this pin useable (DS80448D - pages 3, 15). But this errata states that this problem is applicable only to revision B0, that is relatively old. We have chips of revision B1. Was this issue really fixed in B1? If yes, the work around should not bee needed, but in this case how this feature should be used?

Are there any differences in dsPIC30F3010 and dsPIC30F4011 devices regarding this issue?

I use assembler from XC16 v1.11. The sample code is (the part that sets FOSC):

.section    __FOSC.sec, code
            .pword    0xC701;         // FRC with 4x PLL.

Update:

I made experiments on programming undocumented FPR's into the device. As an environment I was using MPLABX and ICD3. It turns out that compiling always goes fine and the .hex file always contains the values that I put into the code. But some part of the tool chain blocks programming the undocumented FPR values into the device. After programming the "Configuration Bits" tabs shows the value C100 (FRC without PLL) and device works like this value is really programmed there.

The behavior described above (blocking programming) happens to majority of the values. The values 0x02, 0x04, 0x06, 0x08, 0x09, 0x0b, 0x0c manage to get through, but device does not seem to work properly.

These experiments have not destroyed the device.


texts: How do I know if I should use VBUS-sensing on STM32?

texts:
I have a schematic that looks like this.

And I wonder if I need VBUS-sensing on my STM32? Because, I planning to use the +5V from the USB, to power the STM32 and also have communication (D+, D-) with the computer and the STM32. Is that possible even if I power the STM32 with USB-power?
According to VBUS-sensing detection data sheet from ST. They say that if USB device is bus-powered, then I don't need VBUS-sensing. Is my STM32 the USB-device or what?
Assume that I'm using VBUS-sensing, what should it be good for?
Should I connect VBUS directly to PA9 (with a voltage divider) and let it just float? No connection and no CubeMX configuration?
My STM32 is STM32F373 series.


texts: Regulated power supplies - how do they work?

texts:
I'm building a small audio amp (a current controlled varient of the szekeres design) and it apparently needs a very clean, regulated power source. Due to minimum parts order requirements, i'm going to end up with, amongst other things, a spare lm317 and others. As i understand, both the standard transformer-> wheatstone bridge bridge rectifier and switching power supplies are relatively noisy, so since i have parts spare, i'm wondering if following the reference design to build a voltage regulator would make a difference, or if i should just use a switching power supply to power it - i should be able to find a 15-20 v one which i'm planning on using anyway, and not using the voltage regulator at all for power supply

For that matter does using a voltage regulator reduce rippling and noise, or is it just a complicated voltage divider?


texts:
I have a Faulhaber 1717T006SR DC motor with a build-in quadrature encoder.

Here is the relevant bit of the datasheet for the encoder.

The encoder outputs are 5V.
I want to interface this with an FPGA (spartan 7) which takes 3.3V inputs, so I used a TXB0104 (4-Bit Bidirectional Voltage-level Translator) to convert the 5V signals into 3.3V on my custom prototype PCB, trace length is 47mm, width is 10mil on a 1oz copper layer.

I wanted to confirm all was ok first before connecting it to the FPGA (the FPGA development board was not cheap). So I connected it to an STM32F407 (F4 Discovery board) with 5V tolerant pins. I then probed the pin on the STM directly with the probe ground spring pushed onto a ground pad nearby. (I did not use the alligator clip ground lead on the probe)

Here is the result

And zoomed in.

There is a 1.5V overshoot and undershoot, also ringing.

The oscilloscope has 100Mhz bandwidth, the probes are 200Mhz. I used the ground spring on the probe pressed onto GND close the probe tip to eliminate (as much as possible) the effect of the probe on the circuit. At the time of measurement both channel A & B was connected to a STM32F407. I tried connecting the encoder directly to the STM32 Discovery F4 without the level translator and I get 1V overshoot & 1.5V undershoot but there is less ringing.

My questions.

a) Is this the oscilloscope or the way I'm probing thats not correct and causing this. Any advice?

b) If not? How do I deal with this or will this not damage the Spartan 7? (datasheet says max voltage is Vcco + 0.55 = 3.85V on the inputs)

Thanks


texts: I need to implement the short beep sound at PSU being switched On/(Off - if easy). Are there any simple circuits for this problem? The piezo buzzers are preferable of their size and PCB mountable option. But is there any way to run them without controllers? Thanks!


texts: More Options for Reading Thermocouple Signals

texts:
I've tried a few options for reading the signals from thermocouples over the years.

The cheapest way (component cost) is likely to be DIY, and a lot of work involving lots of analogue stuff that I'm not good at!

I've tried the following:

MAX6675

1+     £14
25+    £9
100+   £5

SPI Thermocouple solution
Very easy to use and results are returned with 0.1°C accuracy.
Very expensive

AD597

1+     £6
10+    £4
100+   £3

Feed output voltage into microcontroller ADC
I've had good results with these

Does anybody have any other recommendations?


texts: Why does fuse rating not coincide with max power of device?

texts:
I am reviewing the electrical specs for a few different devices, and I am just confused why some devices have a fuse rating that allows for a higher power input than what is listed as the "max power".
For example, the specs of one device states that it has a max power consumption of 200VA and has a 4 amp fuse.  But with that type of fuse, technically it could allow for a max power of 4ampx120V = 480VA before the fuse blows.  Why not just have a 2 amp fuse or lower to be closer to the max power consumption?  Is this just bad design?


texts: How do i measure watts on single phase power?

texts:
With a clamp on amp meter, I have 8.2 amps at 123.6 volts on one leg and 7.2 amps at 123.9 volts on the 2nd leg. When I touch the volt meter to both legs I get 247.8 volts.

What is the total wattage? I get 3816 watts total if I add the amps together and divide by 247.8 or 1905.5 total if I calculate the watts (v x a) for each leg and add together.

What is the correct way to do this.

The measurement was taken from the two main wires that feed the house panel box from the transformer, so everything that was on in the house was showing in the measurment, there can be an amp difference since single pole breakers only draw from one of the wires.


texts: Manage clearence trough schematic in Altium Designer

texts:
I have a multilevel project to measure different potentials and current. This is done by opto isolated amplifier. The design is similar to the image:

The sheet is reused in upper sheets multiple times.

Question: How can I add clearance rule to the schematic that describe the minimum distance between these component (the connector and only some part of the sheet entry) and the rest of my board?

EDIT:
LabPSIsoInput scheet entry hold an isolation amplifier schematic, so one half of it is on the high voltage side, the other one is on the isolated output.

What I want is to declare clearance rule (at least net class) to the mentioned part of the isolated amplfier, apply this net class to corresponding sheet entry on the image.

I want to do it so that this sheet is generated multiple times by REPEAT() macro on its parent sheet


texts: Coin cell batteries that are 1V or lower?

texts: Does anyone if there are any coin cell batteries that are 1V or lower? I did a Google search and I checked on websites like Mouser, Digikey and find that the smallest voltage is 1.4 or 1.5V


texts: Arduino connecting multiple GPIO pins to one voltage line

texts:
So basically, I want to connect a small Peltier cell to an Arduino. I know that Peltiers are very inefficient and require large amounts of power in general but I only need to create a small temperature change. Anyways, I tried connecting it directly but the amount of current I get from one pin is too little.

I was wondering what would happen if I connected, say, 5 pins as parallel connections on a breadboard. Theoretically, if each pin is giving me 40mA, I should get an output of 200mA. Is this logic correct? Furthermore, if this is true, would I have to worry about reverse current spikes damaging the Arduino?


texts:
Coming from this question, I decided to have some changes. So my case is I have an LED with this description:

Dimensions (diameter x height): 20 x 8 mm
Operating voltage: 3,4-3,6 V
Rated current: 700 mA
Power Dissipation: 3 W
Lighting angle: 120°
Luminous flux: 160 lm
Color temperature: 6500-7000 K
Mounting: Installed on an additional radiator
Glow Color: White

Then I have AA Li-ion 18650 3.7V, 3000 mAh rechargable battery, 21*15*10MM TO-220 aluminium radiator, TP4056 Li-ion battery charger and 2 A, 1 Ohm resistor.

simulate this circuit – Schematic created using CircuitLab

If I'll construct it this way, is everything is gonna be alright? I don't have every detail shipped yet and I'm out of time

UPD: updated my circuit by adding 1S PCB Bms protection board. Will this flashlight work properly for couple of months?


texts: What wattage heating element required for 500 degree Celsius oven temperature

texts:
i have 32 litres OTG oven which is of 2000 watts and can generate Max. 250 degree Celsius .

40 Litre capacity
2000 watts

OTG has 2 heating elements, one at top and one at bottom. so each heating element is of 1000 watts, when i am on broil mode only 1000 watts heating element is used which is upper heating element, so it takes a lot of time to cook food and i am planning replace it with high watt heating element.

replacing with this one

3000W 220V heating element.

ref: heating element

i am trying to achieve high temperature ~ 500 degree Celsius and quicker, as food i am trying to prepare needs faster high temperature.

i have few questions regarding the same .

1) Replacing current heating element with High wattage heating element, will it give me more temperature or same temperature but quicker ?

2) there is thermostat too on the OTG , which has max 250 degree Cesius reading and knob.
Do i have change that too ?
or need to get the external thermometer.
i am only planning to use it for specific food preparation which needs high temperature.

3) whats is the relation in between watts and heat generated by heating element ?

OTG outer body is pure stainless stell, so i dont think their will be any melting issue or something like that .

update:

i was under impression that majority ovens can go upto 500 degree celisus, after checking https://en.wikipedia.org/wiki/Oven_temperatures , i have realized the 250-260 is the highest temperature i can get using oven.

i was trying to get same effect of the "Tandoori Clay Oven" here its says it can go up to 480 degree celsius. https://en.wikipedia.org/wiki/Tandoor

e.g.

after reading answers, i think its a bad idea to use current oven for high temperature like 500 degrees.

the above heating element manufacturer said the heating element can reach upto 200 degree celsius even though its 3000 watts.

so does this mean , it can reach 200 degree quicker ?


texts: Measure ~300kHz Induction Heater RF Power

texts:
I have been tasked to gather data from an old running 335kHz 5kW induction heater system. It has no outputs available to give amperage, power etc. Basically there is an assumption that the unit is not doing a good job of controlling a constant power output. Given a constant power set point.

I was thinking about trying to measure the RF field generated by the unit to determine how consistent it is. Although most power meters for RF are for >1MHz... So I was considering using an AM radio front end design to receive and rectify the RF across a resistor, then log the analog voltage. The image below is a basic idea, obviously I would recalculate L,C to be resonant.

This question is also giving a solution similar... Measuring relative rf signal strength

I don't care about absolute accuracy, just relative. I can mount an antenna on a PTFE plate that will not move, so that controls device distance etc. Any feedback or alternative options?


texts:
(note: Using STM32F407VTG, STM32CubeMX for config, FreeRTOS, and tried both IAR and STM32IDE for compilers/debuggers).
This seems to be a common problem, but the solutions I find either aren't clear enough for a semi-beginner, or just don't solve my issue. I am trying to build an automated test jig. It does samples on all sorts of inputs, outputs etc and there are a lot of functions which are run in a sequence, and return either PASS or FAIL (Just a #define PASS 1, #define FAIL 0).
I have some code which was working ok, then as my program grew as I added more and more test routines, it seemed to not work, but only on a return(FAIL). I found that as I returned from some functions, the STM32 would seem to lock up. return(PASS) always works. Doing some debugging I found it was going into HardFault_Handler, which up till now I'd never heard of. After some googling, same faults people were suggesting the stack size wasn't big enough. I was using the default 128 bytes. So I grew it and grew it and grew it right up to max 2048 bytes. No luck.
Some people suggest to look at the stack pointer and program counter, but sadly I have no idea what to actually look at when doing that. Here is a screen capture with a breakpoint set just before I do a return(FAIL).

This is the after I run the next line.

And finally this is after I enter the HardFault lockup.

Can anyone recommend what I should be looking at to solve this?


texts: Boost converter inductor selection - inductor ripple current calculation based on input current or output current?

texts:
I've a question regarding the inductor selection in a boost converter.
In this TI App note under Inductor Selection on page 3, it is asking to assume the inductor ripple current as a percentage of OUTPUT CURRENT.
This is a general circuit of a boost converter below,

In the above circuit, we can see the inductor is connected to the input voltage. So, should the inductor ripple current be calculated as a percentage of input current? Below, I have attached a snap shot from the TI App note.

In the datasheet of the A80604 LED driver, on page 36, step 4c, they have calculated the inductor ripple as a percentage of the input current.
Below, I have attached the snapshot from the A80604 LED Driver Datasheet.

So, which one should be followed? Inductor ripple current based on input current or output current?
Similarly, for the boost converter forward diode (shown in the above image,) the forward current (need to calculate for the diode power dissipation) would be the output current of the boost converter only, right? It cannot be the input current, right?


texts: Selecting switching regulator components based on cost and performance

texts:
I'm designing a PCB which requires 3.3V and 9V power regulation.  Eventually I plan on building a fair amount of these boards, so I want to plan my design so I'm able to buy components in bulk if possible.  It appears the TPS54308 will fit my needs, and I used Webench Power Designer to generate the following reports with BOMs:

https://filebin.ca/4bTkfT8zP59a/TPS54308DDCR_3.3V_output.pdf

https://filebin.ca/4bTkNflWAyyc/TPS54308DDCR_9V_output.pdf

The major differences between the two circuits are the inductor which costs $1.77 more on the 9V design, and the output capacitors which cost $2.22 more each ($4.44 total) on the 9V design.

I don't understand why the recommended output capacitor changed on the 9V design since the recommended output capacitor on the 3.3V design seems to have the same specs except for voltage rating (25V output capacitor for 3.3V design, 63V output capacitor for 9V design).  Could I get away with using the output capacitor recommended for the 3.3V design on the 9V design?

Similar question for the inductor.  I don't have much experience with inductors, but spec wise, the inductors recommended for the 3.3V design and the 9V design seem very similar.  Could I get away with using the inductor recommended for the 3.3V design on the 9V design?

Also, how can I determine "what I can get away with" in the future as it pertains to inductor and capacitor selection for switching regulators?  I.e., if I'm not using the inductor recommended by TI, would I switch it out for one with a larger or smaller Henry value, larger or smaller resistance value, etc.


texts: How can I sacrifice a bit of DC Voltage to transform it to DC current?

texts:
I made a project with using voltage doubler(which has input of 12V) which output is 43V(I expected 24V) but current is low when connecting the 150 ohm resistor,its about 150mA,but I dont need so much voltage so I need to transform it to current which need to be about 500-1000mA,how can it be done,I heard that you can amplify current with base biased NPN transistor.

Here is the schematic diagram:

I will replace both pots with LM317 and remove R5.


texts: Laplace Transforms and the imaginary input

texts:
When we get an exponential on the RHS of our differential equation (or if we give an exponential input) it's quite easy to solve the equation, but if we provide a sinsusoidal or cosinusoidal input, the calculation becomes horrendous. So we go for a trick, we give an imaginary, complex exponential input and solve the differential equation as usual by assuming \$A \, e^{i \omega t}\$ is the solution. And finally take the real part for a cosinsusoidal input and imaginary part for sinusoidal input (superposition theorem). The only big thing here is finding the complex amplitude \$A\$, once we find \$A\$ we can just multiply it with \$ e^{i\omega t}\$ take real part and arrive at the solution. Here there's a neat trick, when we observe the response in a simple circuit, say an RC circuit we are measuring the voltage across the capacitor. The voltage across the cap is so very similar to an Voltage divider but with a slight change, instead of \$R_2\$ it has a \$\frac {1}{i\omega C}\$

So whenever we are given a circuit with capacitances and inductances, we convert it into an abstract circuit, considering only the complex amplitudes. Find the required amplitude and multiply \$ e^{i\omega t}\$

Now the Laplace transform somehow performs all these neat little tricks in a neat little integral. But I do not understand how, rather I can't relate these two processes eventhough they are the same.


texts: My book says above that there are three essential nodes in the circuit above. I am seeing four essential nodes in total which are marked by those four black dots. Since each of those black dots connect three or more circuit elements? Can someone explain to me how there are 3 essential nodes instead of 4 essential nodes?


texts:
I am trying to send and receive data to and from an STM32F1xx. I have got the STM32 to successfully send data back to the computer. I did that using the code below.

__HAL_RCC_USART1_CLK_ENABLE();
GPIO_InitStruct.Pin = GPIO_PIN_9;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_PULLUP;
GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

//Setup UART RX Pin
GPIO_InitStruct.Pin = GPIO_PIN_10;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

UartHandle.Instance = USART1;
UartHandle.Init.BaudRate = 9600;
UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
UartHandle.Init.StopBits = UART_STOPBITS_1;
UartHandle.Init.Parity = UART_PARITY_NONE;
UartHandle.Init.HwFlowCtl = UART_HWCONTROL_NONE;
UartHandle.Init.Mode = UART_MODE_TX_RX;

//Error handling
if(HAL_UART_DeInit(&UartHandle) != HAL_OK) {
    Error_Handler();
}
if(HAL_UART_Init(&UartHandle) != HAL_OK) {
    Error_Handler();
}
char msg[] = "testing\n\r";
while(1) {
  HAL_UART_Transmit(&UartHandle, (uint8_t*)msg, sizeof(msg), 10);
}

The code above works perfectly. I then tried to send data from the computer to the STM32. I tried the below code

 if(HAL_UART_Receive_IT(&UartHandle, (uint8_t*)msg, 5) == HAL_OK) {
          char msg[] = "HAL_OK";
          HAL_UART_Transmit(&UartHandle, (uint8_t*)msg, sizeof(msg), 10);
 }

and it did not work. No data was sent back to the computer when I sent a byte to the STM32. I did some debugging and the receive function returns HAL_OK once at the start, and then after that returns HAL_BUSY. This makes me think you have to use interrupts, but I am using that with Receive_IT. How do I solve this issue?


texts:
As an emergency responder we learn how to cut open cars and extricate injured or trapped people.  As a part of that, we are taught to always cut the battery cables to prevent stray current flow.

My question: which side is the safer to cut; positive or ground (negative)?  Or does it make any difference?

I have looked for answers on this site within the numerous q & a's about car batteries, but did not see one to help me with this question.

Thanks!!


texts:
I am working on a project with a GPRS and MCU. I am feeding the data to my server via GPRS, it's socket server. I was wondering if there is a way ( AT Command ) to do the reverse, I mean I like to send a command to the GPRS from my laptop, then GPRS feed that to the MCU and MCU take it as a signal, for ex. Turn pin 5 high, or anything.

I was thinking to have a case statement in the MCU so it can translate an incoming signal into a MCU command. Is there a way to do that? Or is it too much of hassle?


texts: Do batteries have a delay when adjusting to a new load?

texts:
So I am creating a battery voltage measure, and it takes a reading both when the battery is in open circuit, and when it is loaded with a 100mA constant current. I have set it up and the reading is being taken right after the load is triggered and I've been getting some rather peculiar readings, at least, peculiar in my eyes.

I'd calculated the loaded voltage to be around 2V less that the open circuit reading (quite an old and used battery) but when I get the readings from the ADC it shows a drop of only around 1.2V.

I have found that if I leave the load on a then measure it with a DVM the output is significantly lower than the ADC reads and closer to what I am actually expecting, so I was wondering if there is some sort of delay in the battery 'adjusting' to the new load, it's all being triggered by a micro-processor so the difference in time between the load being triggered and the reading being taken is next to none as they're one line after each other, I was wondering whether it was the ADC that could have been the problem but after doing some tests I think it is more likely that there is a delay, I just wanted some confirmation of this and also some reasons as to why!
Is is a characteristic of all batteries or just old and withering ones?

Thanks in advance.

Some information on the circuit:
Battery being tested: CR123A
There is a constant current of 0.5mA always over the battery during test, this is what I am classing as 'open circuit'.
The load that is on when I am trying to measure the loaded voltage is a constant current drain, draining 100mA from the battery each time it is triggered.
For arguments sake lets say the triggering timings are as simple as: it is triggered every 25ms -> triggered on -> measurement taken -> 25ms delay -> trigger load off -> repeat.

Edit: This is part of an accelerated life test for a battery so the time before the reading is taken can't really be increased to negate this problem.


texts: Toolchains for STM32CubeMX IDE: what to choose from?

texts:
I just installed the STM32CubeMX (original ST Microelectronics's ARM IDE if I understand right). Once installed I tried to open a new project for a DISCOVERY kit I have (STM32F0DISCOVERY).

Howether after I proceed to Open project I faced with a demand to install a toolchain:

As I revealed EWARM is a full functional IDE by IAR so I was surprised that STM's IDE requires IAR's IDE for its work (besides IAR's EWARM isn't a freeware - it is a very expensive software as I know).

In the project settings window are three choices:

IAR's EWARM,
Keil's MDK-ARM and
Atollic's TrueSTUDIO.

All are very pricey :(

So the questions are:

Is it correct that STM's STM32CubeMX will not gives me any functionality for free?
As I understand from the message, the project can be associated with another tool chain so can I take a look at GCC or any more reasonably priced (of course I'd rather prefer free software) toolchain?
If yes: how can I use GCC with Cube?


texts:
I am currently studying OpAmps and one of the topics that came up was the applications of OpAmp circuits. In particular, I was learning about precision rectifiers (using non-inverting version of it, thus the diode is pointing away from the "out" terminal of the OpAmp). The thing I cannot figure out is how does the OpAmp bypass the Vf limitations that regular full bridge rectifiers face. In other words, say for V_in = 0, the voltage at the inverting terminal is close to 0 as we assume an ideal device. Therefore, the voltage at the OpAmp output terminal is 0.7 volts higher than that of the inverting input. My assumption is that if V_in remains at 0, the voltage at the output terminal will stay at 0.7 volts.

To summarize the question, what properties of the OpAmp cause it to create and sustain that voltage difference that keeps the diode "on". Isn't it just easier for the OpAmp to establish 0 volts at the output and thus 0 volts at the inverting input node?


texts: non-inverting schmitt trigger op amp - replacing a zener diode on the input

texts:
I wonder if it is possible to replace the second figure below with the first one? Would both Vo output be the same on the figures below? If they are different, could anyone explain it by numbers? I don't have a zener diode. I wonder would it be possible to replace the zener diode with resistors/capacitor/inductor/transistor?

Datasheet of the comparator.
Datasheet of the zener diode.


texts:
Currently I'm a it confused. A IC (integrated Circuit) Chip implements one or many circuits on a chip in order to control any kind of stuff.
However, a CPU is from my point of view also a BIG circuit collection. Both are fed with signals in order to control or calculate any kind of stuff.

So when do I call it CPU and when IC-Chip.


texts: Is there any IC which converts 230V AC to 5V DC? As lossless as possible. I want to connect my microcontroller to an ordinary electrical socket and I don't have enough space available. Thanks.


texts:
What is the best way to make a level translator for a led matrix? I have an mcu port 3,3V 5mA and I want to replace the leds with higher voltage and current, 24V 50mA for example

This is my led array

simulate this circuit – Schematic created using CircuitLab

and this is a push-pull level translator I made.
There is a problem in my level translator that allows a current flow through output stage when the input is 0V. I assume this happens because the PNP does not turn off completely. The amount of current is about 20mA at 24V.

simulate this circuit

I would like to be able to choose what kind of LED I use in my matrix. I want circuit to be flexible to choose whatever voltage and current, of course between some limits.

Improved circuit:

Alternative suggestion:

simulate this circuit

I decided to go with first Transistor's suggestion.
First, let me show you how the software control the led matrix.

When a row is pulled high, the corresponding column is pulled low and the other column are pulled high.
In current level of voltages the leds can withstand the reverse bias of -3.3V. But, the push-pull circuit will reverse bias some leds with much higher voltages and this will damage the leds. (If the leds are bidirectional will not be damaged but they will be lit instead).

The solution, according to @Transistor is: A non-inverting high side switch that pulls the row high when the corresponding PIN is high. And a non-inverting low side switch that pulls the column low when the corresponding PIN asserted low


texts: Ripple flowing through probes connected to the same point!

texts:
While trying to filter the ripple of my switching PSU, I've come to a phenomenon that
is probably well known to professionals, but seems absurd to me.
Admittedly, my scope is not of the highest quality, but it can sample at 100MHz and gives usually coherent results.
Furthermore, it is only connected to a floating portable computer working on batteries; so, no parasitic current can flow through the ground or
through another connection.

The phenomenon is the following:
I took an ATX power supply like the one in your desktop computer, and connected the TWO probes of my scope
to the ground wire (the black one) of the PS, AT ITS EXTREMITY A (that is, point A is connected to nothing, except the two probes).
In my scope (set in AC mode), I could observe a small ripple.

As this seems absurd, I first thought this is an artifact, so I connected the first pin of a toroidal inductor (5mH) to A, the ground probe of the scope
to A, and the other probe to the other pin of the inductor (connected to nothing except the probe); surprise ! my scope now show a ripple
of up to 40mV, ranging from 10KHz to 20MHz (centered at 4MHz).
I was trying to explain this to myself by invoking wave propagation, when the next experience mystified me completely:
I connected the ground probe in the other side of the inductor, and the other probe to point A. Then an incredible ripple of up to 0.5V
was shown by my scope !

These experiences contradict everything I know on currents, and in particular, why is there an asymmetry regarding the connection of the probes with respect of the two sides of the inductor (the ripple is AC no?)

I would greatly appreciate any insight.

EDITS:

If I shut down the PSU, while maintaining everything connected as is, the scope shows nothing.
If I don't shut down the PSU, but I disconnect the two probes from the ground wire, while maintaining them connected one to the other, the scope shows nothing as well.
Here is what I believe to be a beginning of explanation: the
electrical wave is exploring the ground wire, and most of it is reflected at the first pin of the inductor. So, between the PSU and the inductor appears a standing wave. At the other pin, few of the AC components of the wave has passed the inductor, hence the ddp between the two pins of the inductor. If there is no inductor, a similar effect appears (but much less strong) because the two probes have a somewhat different inductance. As convincing as this may seem, this does not explain the asymmetry of the strength of the ripple with respect to the pins of the inductor.


texts: Running 3 phase asynchronous motor below nominal torque

texts:
In class we have a 3 phase asynchronous motor which says 400V delta 690V star. The nominal torque of the motor is 3,7Nm. Can the motor run safely nominal charged on 400V in star configuration?

I'm asking this because the nominal torque would be 0,7Nm which is lower than the nominal torque of 3,7Nm.The purple line represents the torque of the motor in star configuration.


texts: How to learn designing electronic cicuits?

texts:
This is a soft question. I have completed my engineering in electronics discipline and unfortunately I still don't have proper idea of designing electronic circuits. But anyhow I want to clear this first and extremely important step of electronic hardware design engineer .

There are various basic components like R,L,C ,diode and other components like IC, Op-amps,micro controllers etc in the circuit. I wonder how circuits are designed for any application (you can consider any circuit of your choice) ?How particular values of such basic components are calculated ? How position of particular component is fixed  ?

Just for example say I want to convert 230V ac input voltage to 5V dc output voltage and 2A output current.I referred Texas Instrument's readymade circuit design which is obtained from webench design software. The circuit have step-down transformer, rectifier, different resistor,capacitors , transistors, fast switching diodes . So I don't understand how these perticular components and there values are selected? How these component are assembled to form a design?

I want to design and build electronic circuits myself. So can anybody tell me how to learn designing electronic circuits ? Are there any good blogs ,books, video series etc that can help me learning it?


texts:
How much nickel is in a NiMh battery?

For example, how much nickel is needed for a 100Wh NiMh battery?
How much nickel is in a common AAA NiMh battery?

This question is equivalent to:
How much lithium in lithium polymer batteries.
It is also asked in:
chemistry.se


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I have an RS-485 input / output from a solar charge controller (SCC) and would like to read the output in two locations, while maintaining its input from one, or hopefully both of those locations (see pic below) everything will be contained within less than a metre square, so distances are not an issue:

Here's the setup - I have an Epever Tracer-BN solar charge controller in place and it has an RJ45 connector on the bottom, which gives data output and accepts some inputs to allow configuration and make read requests of the SSC. There is a proprietary bit of kit to display the output and allow me to change some setting on the SSC, but I would also like to be able to perform the same functions on a mobile app, so need to duplicate the signal to a Raspberry Pi.

The SSC only has one connector, and the supplied cable for that is an RS-485 with RJ45 connectors on it that looks like this:

I can connect to the Raspberry Pi using pins 3&5 or 4&6 into an adapter (link). Can I split the cable by connecting the remaining pair (4&6 or 3&5) into the proprietary monitor, or is this likely to cause problems, for instance because the signal will be... weaker? in some way broken?

I get that this is not a set of hardware that many people are probably intimately familiar with, but I am entirely unfamiliar with any of this stuff and I reckon that anyone who has a good working knowledge of the way these cables and information happens will be able to make a better judgement call / best guess than I can! I'm worried that there might be general problems associated with splitting a cable in the way I suggest.

I am particularly concerned because all the hardware I can find on the internet to do this apparently simple job is exorbitantly expensive, which makes me think that actually it is a very complex thing to do and I must be missing something. All the similar projects for specifically solar setups do not split the RS485 cable so again, I worry that there may be some reason why doing so is impossible.

Any thoughts or advice would be extremely welcome! The basic question I am asking is "do you think this will work, or do you foresee some potential problems I will encounter trying to split this cable?"


texts: What will happen if I connect a 9v ac input with a step down transformer (80V ac to 24V ac)?

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I'm doing a university project and we're not allowed to use mains. Hence, I planned to use a 9V input and step it up to 24V.

However, I couldn't find any transformers online which have a 9V ac input; all I found are designed for mains (220V/110V).

I'm using a switch mode circuit to convert the 9V dc to 9V ac, then step it up to 24V ac and use a rectifier circuit to convert it back to dc.

So my question is what will happen if I bought a 80Vac "input" to 24V ac "output" transformer and used a 9V ac as the input?

I know the voltage will lower in the secondary because the voltage is much lower in the primary. If that is so, how can I calculate the difference?

Also, I'm using a voltage regulator (0 to 40V input) -> (24V output) after the rectifier circuit. Any solutions? Thanks in advance.


texts: How do I read these blasted five-band resistors?

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I have 500 resistors designed like this:

That's brown, red, black, black, brown. Roughly equal spacing between all bands. 120 ohms, right? No. This is a 10k resistor: brown, black, black, red, brown.

Why would they label it this way? They could easily have labeled it brown, yellow, SPACE, brown and it would be obvious how to read it. Am I missing some technique?


texts: Sallen-Key with fully-differential output -- options?

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I have a single-ended audio signal that I want to low-pass filter and convert to differential (with GND as the OCM voltage — that is, when one output is X Volts, the other output shall be −X Volts).

Can I accomplish this with just one fully-differential amplifier, for example the LME49724?  I'm trying to avoid one additional stage in the signal path.

One idea that comes to mind is to just pretend that I have a normal (non-differential) op-amp where I treat the non-inverting output as if it was the output of a normal op-amp and build a Sallen-Key circuit; then, simply use the inverting output as part of my differential pair, without connecting any feedback network from it.

Will this work?  Normally the fully-differential op-amps use symmetric feedback networks.  However, as I understand, the differential amplifier internally forces the two outputs to be the complement of each other, so it seems intuitive that it will work.  Since the input is single-ended, I don't see any issues with common-mode signals (which is what I've seen as the possible issue when there is a mismatch between the two feedback networks). However, a quick LTSpice simulation using the LTC1992 seems to disagree with this — the non-inverting output looks ok, but the inverting output saturates.

How do I make a Sallen-Key filter with fully differential outputs?


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I am thinking of making a portable refrigerator with the above schematics, but I am doubtful that the aluminium frame would be enough of a Heat Sink on it's own.

All the peltier elements are of same dimension (40x40x3)mm ~ (40x40x3.5)mm with 12VDC operational voltage and 6A max current.

Is there a way to know how much cool it will be and if the heatsink is enough or not?

If the heatsinks are insufficient, how should I improve my design? I would not prefer to add fans/water cooler etc until and unless there is no other way out!


texts: vhdl port declaration with different sizes

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I'm writing a vhdl model and I'm stuck with a problem about port declaration.
Let's say that I have an entity entityA that instantiates N entityB. Now, entityB has a port, out, with size M bits, and M can vary among all entities, so out is std_logic_vector(M-1 downto 0). These ports need to be propagated outsize entityB.

If all entityB components would have the same port size, say FIX_M, the solution would be to use a std_logic_vector(N*FIX_M-1 downto 0) in entityA. My problem is that the size M can vary. The first solution that comes to my mind is to use the same solution, using instead of M a MAX_M, but in that case a lot of pins would be left unused (and for input it is a problem, right?).

Do you have a better idea?
Thank you in advance.


texts: I have a logic gate that needs a high(1) or a low(0) to one of the inputs going into the logic gate. In the picture on input A going to the nor gate you can see that one of the inputs says 0, and on input F the nand input says 1. How do I generate this?


texts: Can this circuit produce 0, 5 and 12 volts in fixed increments for the AT89LP4052?

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Due to the speed requirements of my project, I'm looking at replacing the AT89C4051 with an AT89LP4052 with some code modifications since it offers double the memory and 6x the speed for the same crystal.

I'm in the process of making a parallel port programmer for it. Since the port has only 4 output lines (other than data), I'm trying to save some wires in my design and I'm trying to come up with a good circuit that satisfies the strict requirements to prepare the IC for programming.

The following has been taken from page 61 of the datasheet:

Power-up Sequence
Execute the following sequence to power-up the device before parallel programming.
1. Apply power between VCC and GND pins.
2. After VCC has settled, wait 10 µs and bring RST to “H”.
3. Wait 2 ms for the internal Power-on Reset to time out.
4. Bring P3.2 to “H” and then wait 10 µs.
5. Raise RST/VPP to 12V to enable the parallel programming modes.
6. After VPP has settled, wait an additional 10 µs before programming.

Power-down Sequence
Execute the following sequence to power-down the device after parallel programming.
1. Tri-state P1.
2. Bring RST/VPP down from 12V to VCC and wait 10 µs.
3. Bring XTAL and P3.2 to “L”.
4. Bring RST to “L” and wait 10 µs.
5. Power off VCC.

I want to satisfy both of the above requirements automatically in my circuit without using an external switch, button, jumper, or any other control pin.

I came up with the following:

The idea behind this is that both CLK inputs on the IC are simultaneously driven together by an external clock running at 50Khz (Let's say a 555 timer in astable mode). The POWER_STATE input (to the first D line) is meant to do just that... turn the output voltage from 0 to 5 then to 12 every 20uS then be stuck on 12V. When D = 0 then voltage goes from 12 to 5 then to 0 every 20uS.

The transistors are both 2n3904 but somehow I feel something is wrong with this circuit.

Question is, Is this circuit OK? and if so, is 50Khz an OK clock frequency or would it produce interference during chip operation?

And could this circuit be simplified more with common components?


texts: Can lack of grounding affect appliances?

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Grounding is done because if charge leaks the external metal body of the appliance risking the life of anyone who touches it.

But, does this charge leakage, of itself, affect the internal workings of an electrical or electronic appliance?

Could I be required to get an appliance repaired, because my house electrical network system lacked grounding?


texts: Unknown connection to digital counter 4060

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Hey friends! I'm supposed to build this circuit but I'm not really sure what should I do about the thing that is inside the red circle I marked.
Original site is here:
http://www.eeweb.com/blog/extreme_circuits/dicing-with-leds
I have no idea what that triangle means and where does it connect with digital counter 4060. I'd appreciate some explanation. Thank you!


texts: Help understanding voltage limits in a PNP transistor

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As seen below, I have a circuit that turns on +12V to the EN pin of a LM53601 buck converter when the +6V DC component in a car speaker wire is detected (bridged output). This works fine.

But I am a bit confused when reading the specifications for the PNP and I need some help understanding how much voltage the 3906 can withstand. In my current circuit, the +12V from the battery has TVS diode protection, clamping the voltage at 36V. It also has a 200V Schottky in series.

Will a transient of 36V at Q2 emitter destroy it?


texts: Accidentally downmixed stereo to mono, why does this work?

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I have a cheap Chinese Bluetooth audio amplifier like this:

It has four screw terminals for the speaker connections, namely L+, L-, R+ and R-. I accidentally connected a single speaker to L+ and R-, and was surprised to find that I could hear both the left and right channel over the single speaker. I decided to experiment and found out that if you connect the speaker the proper way (so either to L- and L+, or to R- and R+) it would only play the single channel you'd expect it to play, but if you connected either L+ and R- or R+ and L-, it would "downmix" both stereo channels to a single channel and play them both over the single speaker.

I've been trying to wrap my head around how that works, but I can't figure it out. Is the board more sophisticated than I expected and does it output mono when it discovers no load on the different terminals, or is there something else going on?


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Since all kinds of flash memories feature different transfer rates according to the kind of operation performed at a given moment (e.g., random access reads versus random access writes, random access reads versus sequential reads, etc), could SSDs be considered as random-access devices?

Of course, if the access time (latency) is not the same for all operations (as definitely it is the case with SSDs), in principle neither SSDs or any other flash-based storage device should be thought as random access. On the other hand, the latency for a given access is independent from prior accesses: you are supposed to access any memory position you want by simply presenting an address in a given bus (as opposed to search for markers between records stored sequentially, as it is the case with tapes). In fact, many people wonder how long is gonna take for flash-based storage devices replace RAM sticks. So, should flash-based devices as SSDs be thought as "true" random access devices?


texts: How can I discharge a fully charged 450V 47uF capacitor?

texts: Yesterday I had laptop charger opened and take a closer look at it. And went for capacitor because it looks damaged. Then the new capacitor is replaced, plugged in and doesn't work. I don't know if the MOSFET is dead but I saw smoke coming out. The capacitor is charged like almost full and it's getting messy dealing with the circuit. Can I discharge the capacitor safely with a resistor? Ff so, what value/wattage of resistor should I choose for discharging 450V 47uF capacitor?


texts: Is there an English word for the output response of a non-minimum phase system?

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I've noticed in some French language control courses they have a word for the initial part of the response of a non-minimum phase system.  They say it has "un départ malin".  I looked up malin and it means different things in English, for example:

foxy, canny, crafty, cunning, sly
Google translate: "a smart start".

There are plenty of descriptions of the step response of such a system: the initial direction of the step response is opposite to the final value, it goes in the opposite direction to the long-term response,

but is there a better equivalent English word to 'malin' that people commonly use to identify the non-minimum phase system response characteristic?
I've also seen the word 'undershoot' used in this context but I'm not sure that's correct.


texts:
I have a PIC16 for which I have the (asynchronous) UART transmit working just fine, but the UART receive producing invalid results.

For example, a gets interpreted as O, b gets interpreted as ', and c gets as N.

Here is my receive function:

char UART_read(void) {
    while(!PIR1bits.RCIF) {}

    return RCREG;
}

My hypothesis is that the UART polarity is wrong for the receiver, so that in particular the start/stop bits get messed up. I have set the SCKP bit (see page 302) to invert the data on the TX/CK pin but I cannot find an equivalent for the RX/DT pin.

What could be the cause of the UART receive not working? How can I invert the data on the RX/DT pin?


texts:
I work on commercial food processing equipment. With a schematic, I am somewhat useful but without one I am generally lost.
I just received a German machine that is a dual capacitor start/run machine. The company is no longer in business and documentation is non-existent, with the exception of the one drawing I found after weeks of searching. The problem is the wires were removed from the switch when I received the machine and the switch on the machine is not the same model as the schematic.
I have attached the drawing but I don't understand the switch function. If someone could explain the positions on the switch (I know where power comes in and that common bypasses the switch) but I don't understand the different functions. Thanking you in advance for any help, in this matter.


texts: What value of C should be added in parallel to make the circuit appear purely resistive?

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I'm currently working through Cogdell's Foundations of Electrical Circuits and came across problem 4.39 d) as shown below:

Earlier in the question I found the frequency-to-be-used as 43.3x10^3 rad/s. Now, in order to make the circuit appear purely resistive the reactive part needs to sum to 0. In part c) of the question the capacitance was being added in series, so I simply used wL-(1/wC)=0. For d) however, the capacitance is to be in parallel with the inductor, leading to the (seemingly) unsolvable equation:

The book says the answer is C=0.1uF, and that it should lead to a real impedance of 400ohms. The only approach to this question I haven't taken is using the formula for the impedance angle for an R(L||C) circuit, but I'm not actually sure what that formula is. Any insight or hints are appreciated! Thanks.


texts: Inductor core loss for H-bridge type inverter

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This is not a question about a specific circuit, rather this is a question about a concept.

In a typical switching H-bridge type inverter, which currents contribute to the core loss of the output filter inductors L1, L2?  For the sake of this question it doesn't matter if it is a bipolar or unipolar inverter.

simulate this circuit – Schematic created using CircuitLab

A) 60Hz load current

B) Switching ripple current

C) Both 60Hz load and switching ripple current


texts: Why does my 12V SLA Battery behave strangely when charged by simple LM317 circuit?

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I'm currently working on a DIY alarm circuit and I have need of a charge controller for a 12V SLA battery.
I picked up a XH-M603 charge controller (https://www.banggood.com/XH-M603-DC-12-24V-Charging-Control-Module-Storage-Lithium-Battery-Charger-Control-Switch-Protection-Board-With-LED-Display-Automatic-ON-OFF-Real-Time-Voltage-Monitor-p-1250279.html?akmClientCountry=GB&cur_warehouse=CN) to help with the build and realized later that this module will determine when the charging source gets turned on and off, but doesn't actually control the charging voltage or current (I'm new to charging circuits, so I'm learning as I go).  So, I still need to build a charging circuit that delivers a controlled (voltage & current) charge.
Looking around for example circuits, I came across this one in the LM317 datasheet:

This circuit doesn't work for me and I think I understand why.  But to prove to myself that my brand new 12V SLA 7Ah battery wasn't a dud, I used a slightly different technique using a bench power supply (constant voltage - 14.7V, current limited to 0.7A - 0.1CA with protection diode).  The bench PSU worked as expected. After an initial surge of current that triggered the constant current mode of the PSU, the charging settled down and the voltage on the battery rose slowly from 13.4V. The current flowing was much less than 0.7A.  Wonderful.  The XH-M603 wasn't connected in this setup.

The LM317 circuit has entirely different behaviour! The first time it's connected the maximum current of around 0.7A flows. The voltage on the battery starts at 13.4V but then quickly rises to 14.7V at which point the XH-M603 limit kicks in and switches the charging off. The voltage detected by the XH-M603 now returns to 13.4V and as that's below my preset minimum voltage of 13.7V, it activates the relay and turns the charging back on.  This time (and subsequent times), the voltage rises very rapidly to 14.7V and the XH-M603 just cycles off and on.  Not great.

Looking at this simple LM317 circuit you can see that it limits the current by altering the voltage at the output.  So, the key difference between this circuit and the bench PSU is that the voltage changes between full current limit and a lower current.  The voltage is aound 13.7V when 0.7A is flowing, moving to 14.7V as less current flows.  This is not a constant voltage charger.

I can fill in the exact values I used for the resistors in the LM317 circuit later, if that's important.  I don't have them to hand right now, but the sense resistor is around 0.8 ohms and the divider assumes 14.7V when the transistor is off.

What I'm looking to understand is what causes the battery to behave as it does when the voltage moves around like this?


texts: General Peltier (lack of) cooling - why?

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The physics here are beyond simple.

1ml of water requires 4 watts of cooling to drop 1 degree C.

Thus:
30ml x 4W x 33c = 3.96kW (IE cool 30ml by 33c needs 3.96kW of cooling)

The TEC01-02015 spec sheet shows that at even the meager 12V output at max amps available, shows 33c is the rated dT and the Qc is 100 W. It does not say Qc is per per hour or per minute, so we assume it is constant.

3.96kW divided by 100 W/s = 39.6s OK. Round to 40s.

The TEC is well cooled... the cold side is showing -17c in the aluminum water container attached to the cold side.

WHY can't we simply cool 30cl of water without it taking an hour or more? Yeah, sure, there are losses to the ambiance and to the container holding the water (aluminum). What else are we doing wrong?


texts: Why don't the fuse connections in programmable ROM cause the whole matrix to be shorted together?

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If the rationale of using diodes in ROM (rather than simple wires) is to prevent the matrix being shorted together, then why does shorting not occur for programmable ROM - which has blowable fuse connections?

Apologies if should not be starting a new thread for this; please note that the question is inspired by an answer here What is the rationale of using diode matrix in ROM , but I don't have sufficient 'rep' to comment my question there.


texts:
I was planning on having a couple of solar cells recharging a battery!
My question for this is:

How can I recharge a battery through solar cells and at the same time let the battery do some work(Because if I setup some solar cells to the battery and then from there to let's say a lamp, then how can I be sure that all the solar cell's energy goes to the battery FIRST and THEN to the lamp)?

And how can I know if a battery is nearly full(So I know when to switch batteries)?

If I am not really clear about the question's then please say so :)


texts: How to understand rail to rail input circuit?

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I watched an input circuit for ground rail as follows,

Why do I have to place a current source here? If I place a resistor instead, there will still be current flowing in emitter-base direction for ground input at IN+.

Similar rail-rail input circuit bothers me as follows,

What signal will port 1-4 have when IN+ changes from 0 to Vcc? And why?


texts: I want to attach a heat sink to the inductors on my motherboard, which glue could I use?

texts:
If I wanted to attach a heat sink to the inductors on my motherboard, which glue could I use?

I have a Gigabyte A320M-S2H, this motherboard has heating problem when used with the AMD ZRyzen 7 2700X processor. I believe that only a heat sink would solve this problem.

If you search the internet, you will find that the vast majority of motherboard models for this processor already have heatsinks.

Here is an example:

Is the heatsink on the mosfets or on the inductors?

I found a good image to explain this problem

Here is my problem

My processor is throttling to 500 Mhz


texts: Output capacitance effect on stability of DC/DC Buck Converter?

texts: How does having more or less capacitance at the output of a DC/DC buck converter contribute to the location of the poles and zeros. Is there a way to crudely make this calculation.


texts: K2554 transistor - is it equivalent to 2SK2554?

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I have K2554 transistor. There is a symbol similar to Hitachi logo. I can't find datasheet for it.

Is it equivalent to 2SK2554? Can I rely on 2SK2554 datasheet?


texts: Hooking audio compressor to mains without chasis

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I am nearing the completion of my DIY compressor project, and I have a rather seemingly basic question..

Once I hook up my toroid and everything, since I don't have my 19" 1U rack enclosure yet, but would like to test my projects for any problems, is it safe enough to find a metal piece somewhere, put a lug, and attach all my grounding to it?

I should also add that the compressor is the GSSL project and is all solid state design. No tubes.


texts: Parsing .s2p data through an automation script to plot graphs of the various s-parameters

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Need to find a way to quickly decipher and plot s-parameters for tons of .s2p files in a short period of time.

In specific, I need to plot the angle of the s-parameters versus frequency and then the amplitude of the s-parameters versus frequency.

There needs to be a faster way of doing this. Any ideas of programming this in an automation script (python or MatLab is preferred).


texts:
been using picaxe for a few years but now playign with arduino and trying to learn how it all works.

I have a couple of arduinos talking via the HOPERF library successfully and now want to send some meaningful data over the link.

I have the code for the DS18B20 running on the client aurduino and "printing" the temp value to the PC via USB but just not sure how to get it into the HOPERF commands to send over the RF.
Here is a bit of the code. The 2nd line is where the data is sent over the HOPERF.
What i need to do is replace the string "test" with the data returned by the (sensors.getTebyCByIndex(0)) command from the 4th line.

sensors.requestTemperatures();            // Send the command to get temperatures
client.sendto(11, (uint8_t*)"test\n", 6); // Includes the NUL at the end of the string
Serial.print("sending\n");
Serial.print(sensors.getTempCByIndex(0)); //prints the temp value over the USB

Any clues anyone?? I prefer to learn but doing stuff like this - and yes i did do the "BLINK" thing first! I find doing something i find useful helps me learn faster :-)

I am struggling a bit with working out the docs as there doesnt seem to be a nice "manual" liek the picaxes to follow :-(


texts: Why doesn't the following circuit have negative feedback?

texts:
Consider:

The Sedra book says that it's a Schmitt trigger, so there is positive feedback, but why doesn't it have negative feedback as well?


texts: I've been looking into batterie's datasheets and don't understard what 2 of the specifications mean: continuous standard current and maximum continuous discharge current. Could someone explain this to me?


texts:
I'm playing around with BJT amplifiers and have some questions regarding the gain rolloff you see at higher frequencies, I'm using the 2N2222 for my tests and my simulations and measured results match up pretty well, example below:

So at 3MHz or about I see my rolloff start affecting my gain, which is described in another answer, at around 18MHz the gain drops to 0dB. My questions are:

Is this rolloff caused by the Miller effect?
If not caused by the Miller effect what is the cause?
Can you compensate for the gain rolloff to some extent or do you need to choose a faster BJT?. I've played around with the input impedance which I thought would help but this made little difference.


texts: Why do older (green) PCBs have primarily a darker color, whereas new ones are lighter

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Note the difference in color between this old commodore board and this newer board. It might seem like lighting, but after looking at my own collection of scrap boards, the older ones tend to have a much darker color than the new. I thought it might be aging on the mask, but all the old ones essentially have the same color, so I thought it unlikely.

Does anyone know the reason for this color change?

Is it a change in board material, masking chemicals, etc?


texts: How do gamepad buttons interact with the PCB?

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How do the buttons (like A, B, X, Y, and D-Pad) on game pads (such as the Xbox controller) interact with the PCB? If my question sounds vague, refer to the pictures below:

Are A/B the same as C/D? In game, the D-Pad (left) shows up as "Axis", while the buttons (right) just show up as "button".

What are A/B/C/D called, and what are they made of? It all looks and feels like rubber, but if that were the case then it wouldn't have any effect on the electrical properties of the PCB in that area (right?).

How does the logic of A/B and C/D work? How does B pressing on A (or D pressing on C) send a signal to the computer saying "button X has been pressed"/"D-Pad UP has been pressed"?

For reference, I know how a push-button works; it makes and breaks physical connections, which in turn impedes or allows electrical current to flow. But I can't see how that happens in this picture.

Also, here's a picture of the other side of the PCB (it might help).


texts: Execute instructions from RAM in a hobbyist-friendy microcontroller

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One of my projects would greatly benefit from being able to run a program that isn't stored in the microcontroller (but is instead stored in a SD card).

So, I'm looking for a device that will allow me to load the code from the SD card into RAM and then execute the code from RAM. Currently, I only have the programmer that comes with the PicKit2, so I'd prefer to stay with PICs.

Does anyone know which, if any, PICs can do this? If no PICs are capable of this, then what are some different micro controllers that would work for this? Preferably ones that are available in a breadboard compatible package.


texts: Digital potentiometer, initial (wiper+start position) resistance compensation

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In my project I am using a LT3086 (40V, 2.1A Low Dropout
Adjustable Linear Regulator with Monitoring
and Cable Drop Compensation
)

With this voltage regulator you can "programm" the output current limit by connecting the pins Imon and Ilim and by setting the resistor Rmon to a correct value. (as shown in the picture above)

The relation between resistance Rmon and output current limit Ilim value is given by this equation (datasheet page 13):

Ilim = 800/Rmon

My goal would be to control the current limit between 5mA and 1A, where:

Ilim = 1A  at Rmon = 800 ohm
Ilim = 5mA at Rmon = 160 kohm

My initial plan was to implement one digital potentiometer with a value 200K and with 256 steps (781.25 ohm/step). Since the equation for setting the current limit Ilim is not a linear function, you can not get a good resolution for the higher current values, but as you get higher in resistance the resolution gets better.

To counteract that, my plan is to implement a series of digital potentiometers (256 step) to simulate a digital logharithmic pot (I couldnt find any log pot that would sufice).

simulate this circuit – Schematic created using CircuitLab

And this would all work fine in ideal conditions...but the world is not ideal. 800 ohm resistor would be used if there was no wiper resistance and no 1. step resistance (when there is address 0). Wiper resistance can be between 75 and 300 ohms.

So by using 5 digital pots in series at address 0 and with the wiper resistances, in the best scenario, I would get around 1023 ohms.

R=75+3.9+75+19.5+75+39+75+195+75+390=1023.4375

By putting it in the equation, the maximum current limit and with that current at all, I could control with that would be:

Ilim = 800/1023 = 0.782 A

Which is far from 1 A.

Finally, the question:

How would I precisely compensate for the wiper+1.step resistance to get the resistance of 800 ohms, so I could set the current limit upto 1A?


texts: Designing a schematic for PCB, what should I consider?

texts:
I'm drawing a schematic of 12V LED strip dimming switch board. Below is a summary of how it works:

A DC adapter (12V 2A) will power the board.
A controller inside (ESP-01) will be powered by 3.3V regulated output.
Output of the board is connected to the LED (consumes up to 1A,) and will be controlled by the controller's PWM output.

I'm planning to design a 2-layered PCB. However I'm very careful because I have failed twice previously.
Are there any problems with the schematic below? What are the common issues with these kind of applications?
Edit 1
Schematic updated. Thanks @Transistor.

Edit 2
I didn't want anything to be 'attached' to my board, so I decided to design the power supply for the controller, too.
I have other applications using NodeMCU or Lolin D32, which are very easy to handle, but implementing a single switching board using self-powered ESP-01 (requires no power supply than the 12V adapter) has long been my personal goal.
I forgot that the gate of the transistor sinks current and pulls down GPIO2 on boot. I'll update the circuit when I fix the problem.
I once used a low-side N-channel MOSFET and got a problem. So I decided to place a P-channel MOSFET at the high side and control it with NPN transistor.
Actually I found a board from Aliexpress that serves the exact function I need. I'm now waiting for the shipping. As @KD9PDP mention in the comments, it would be a great template I can learn from and build new things on.
Edit 3
I've posted this question because I have failed at a previous revision of the circuit above with randomly flickering LED and didn't want to make any failures again.
As @SimSon mentioned, the low side MOSFET doesn't seem to be the problem. I think I have some mistakes in the layout. Here is the schematic and the layout,
I have another question:
I'm going to use K7805-500R3 in my next revision. The datasheet says two capacitors on each input and output terminal are required, like below:

They also suggest two more things which are:

a circuit where an LC filter is placed on the output terminals.

and an EMC compliance circuit.

What are the benefits of adding an LC filter to the circuit, or following the reference of the EMC compliance circuit? What risks do I take when not following them?


texts: MMC/SD card interface - any access to wear levelling info? (counters, etc)

texts:
I don't suppose there's something in the MMC/SD card specification for retrieving any information on erase counts on an MMC/SD card, is there?

My goal is to get my embedded system to avoid writing to metadata like last access or modified times, allocate moderately sized files filled with 0xFF sa needed, and only append records within that.

This is to reduce the risk of data loss, since power can be lost at any time.

However, the wear-leveling algorithms of MMC/SD cards is an unknown, and possibly implemented very poorly.  I need to verify that the cards don't attempt to erase data blocks if I'm only writing data over 0xFFs. So, if there was just about any kind of erase count (total for the disk, per block, whatever) available to read...  that'd be great.

I'm not entirely sure where this question lives... but since it involves SD card protocol level stuff, I figured maybe here.

EDIT

I believe I will go ahead and overcomplicate things. Disk tests proved that at least the SD cards I have will erase blocks even if the data you write is unchanged from the contents on disk. I'll store up to 128KB of data in directly controllable NAND (which I can control write behavior somewhat better on), then write 128KB chunks into a 128KB-aligned file on the VFAT partition. That should limit the exposure about as much as possible... but wow how ugly and complicated.


texts: i have a 48V output. I want to connect a load switch to it so if i put a 3.3V signal to the load switch. the load on the 48V line will be 3A. I don't know how to do this correctly.


texts: Choice of bypass capacitors for PIC18F4455

texts:
Does anyone know how many and what values of bypass capacitors I need for a PIC18F4455? The datasheet does not provide any information on this and I don't want to use more than what I strictly need, given that I don't have much real state available on my PCB.
Also, if anyone has good guidelines for choosing number/values of bypass caps for MCUs in general, I'd also appreciate that.

Thank you,
Chris.


texts:
So, my problem is very simple: I need to use an Arduino to control whether or not my circuit is open or not.

However, I need a low resistance (less than 1 Ohm, hopefully) switch (Relay, Transistor, I don't really know what to look for) that lets a 4A current through.

I have a 8V battery that I need to connect to a 2 Ohm (can be tweaked slightly according to the switch's resistance) load at certain times, but so far I've fried everything I tried.

I used the N-channel MDF5N50B transistor with these characteristics and a few relays that I was 99% sure would fry, and fry they did.

What should I look for in the component?

I searched some electromagnetic relays but they all seem to require a higher current than the Arduino provided one to function.

It's ridiculous that I already took 3 electronic courses in uni and for all the theory on transistors I still have no idea what to look for.