texts: Connect multiple earphones (with microphone) to one computer

texts:
I would like to connect up to 4 pair of earbuds (the in-ear type, stereo, with a TRRS connector and a tiny condenser microphone located along the cable, think iPhone wired earbuds) to a single computer, an Apple iMac.
The signal from the 4 microphones should be merged (added) into the single Mic input on the computer, and likewise the stereo output should be used to drive all 4 pairs of earphones. I would like to additionaly have 4 potentiometers to act as independent volume controls for the 4 earphones.
The 4 earphones will be the same exact model. This is the simplest diagram I could come up with (it only shows 2 modules for brevity, but the final design would have 4):

Would this be suitable? Would it damage the PC input in any way? What values would you recommend for Rn and VRn?
Do you think I need an active stage (op-amp) in either the mike and/or stereo output signal paths? I fear I will need an active amplifier at least in the output, otherwise the volume might be too low. In that case, could you recommend a suitable IC and schematic for the amplifier circuit?
Additionally, this setup will be used with each socket either having an earbud plugged in or not at any given time. So if I add op-amps, do I need to power them on based on the plugged in status of each jack? Again, if you could point to existing schematics, that would be very helpful.
Thanks in advance!


texts: Determining state-of-charge of a lead acid battery under load

texts:
I am trying to implement an extremely simple lead acid battery state-of-charge (SOC) estimation calculation. The following values are known:

\$V_F\$ for SOC=100%: Open circuit voltage of the battery when full
\$V_E\$ for SOC=0%: Open circuit voltage of the battery when empty
\$V\$: The real-time terminal voltage
\$I\$: The real-time load current

Using \$V_F\$ and \$V_E\$, if you know the present \$V_{OC}\$ (open circuit voltage), you can calculate the SOC using this simple formula:

$$
SOC = \frac{V_{OC}-V_E}{V_F-V_E}
$$

A common issue, and my problem, is that I can't afford to stop using the battery long enough (up to 12 hours according to some of the literature) to get a stable read on \$V_{OC}\$.

So, can I use the load current and terminal voltage to approximate \$V_{OC}\$, and then calculate the SOC?

I'm fine with a rough estimate (80% accurate or so), and possibly some method which calibrates periodically whenever I know (by some other means) that the battery is full or empty.


texts: Can inductor voltage and capacitor current change abruptly?

texts:
I understand that inductor current and capacitor voltage cannot change abruptly, but can inductor voltage and capacitor current change abruptly?

I have a feeling the answer is no but I cannot explain why.


texts: Difference between Mosfet and Voltage Regulator?

texts: I'm new to electronics and was wondering what was the difference between a Mosfet and a voltage regulator?


texts: What PCB wire termination should I use for high-vibration environments?

texts:
I'm designing a system for a high-vibration application. I need to land wires on circuit boards. Someone suggested that I use a Wago cage clamp, and that there might be similar things from other manufacturers. The cage clamp was described as useful for this application because the more the wire pulls, the tighter the clamp becomes.

I'm thinking that this might be the same as a spring cage, tension clamp connector. Is it? Is either of these things the "correct" terminal to use for this kind of application?

added: Vibrations are 0.4g peak-to-peak @ frequencies up to 100 Hz


texts: Can we mix pwm and resistor to control brushed dc motor speed?

texts:
In my car the blower motor speed is controlled by 4 valie resistor pack.
I want to have fine tune speed control so I am planning to add a pwm fan speed controller ( Generic).
My question is if I connect the resistor pack input to the pwm controller input and pwm output to the blower fan( without removing the resistor pack).
My concern is if I connect both in parellal (resistor and pwm controller) will it work?
Will that damage the pwm controller even if I use a diode at pwm output  to prevent the voltage coming back to the controller?


texts: I'm powering an attiny45 from a single lithium ion battery; that when fully charged should have a maximum voltage of ~4volts and will be cutoff at 3volts. I was thinking I should be safe to just directly connect the attiny to the li-ion battery, am I right? Or am I missing something?


texts: How do devices that are rated for 120/240 volts work?

texts: I am about to go over seas and when considering powered items I am bringing, some things state they can take both 120 and 240 volts.  What do devices usually do to make sure their output is the same given either input?


texts:
I want to strobe a typical Chinese 100W LED chip on about a 20:1 ratio so that I only use a little over 5W of power.  This is so a camera system can get a colour picture at night so a noticeable flashing isn't a problem.

I'm thinking of having a 33V PSU that charges a capacitor up and then this is discharged into the LED until the voltage drops enough to turn the LED off, whereby the cycle will repeat.

Has anyone flashed these LED chips and know what speeds they can be flashed at and still give full power ?


texts: What is the standard way to represent fixed point numbers in VHDL?

texts:
Is there a native type in VHDL language similar to std_logic_vector that allows one to create a signed or unsigned fixed point number for given length of fractional and whole parts? If so, can it be synthesized?

How does one see fixed point quantities in wave window in test bench? Does one need to create a variable of type real and then use it to represent the fixed point quantity after manual conversion?

Are there functions in VHDL 2008 for conversion to and from fixed point and VHDL real type?


texts: Configuring the sampling frequency on STM32F4

texts:
How do I calculate the ADC Sampling Frequency if the (12 bit) ADC Clock of the MCU is 36MHz with a prescalar of 2?

I use a SysTick Event Handler to sample every 0.25 ms for example.


texts:
My Precor M9.23 treadmill stopped working, and after reading the troubleshooting manual and looking at the motor control board, the led indicated that the board is bad.  Upon removal of the board, I saw that one of the diodes had failed (blown open).  I can't see any indications on the diode to know what to replace it with, but attached is a close-up image of the blown diode, a similar circuit board with the diode intact, and a close-up showing the intact diode in question (small black/gray cylindrical, I believe uni-directional).

2 questions, should I attempt to replace the failed diode, or is it's failure likely the result of some other failed component?  I'd rather not replace the entire board if possible, it's ~$300 US.

What can I replace it with?  I can't make out what the markings mean. It's roughly 10 mm in length.

I've tried looking for the circuit diagram for this board, or better pictures of the TVS diode, but no luck.

Thanks.


texts: I need an edge-detector to put out a single high pulse on the rising edge of a signal (which will then remain high for an indeterminate amount of time).  The purpose of the pulse is to trigger the set on an RS latch, which will then be reset at some point later.  Resetting the latch will indirectly cause the signal going into the edge detector to return to a low state.  I found several designs, none of which were exactly what I need.  I would like to create the edge detector completely out of 74xx series ICs.  Any help with this would be appreciated.


texts: why discharging capacitor voltage in a rc circuit is positive? why it should not be negative?

texts: During discharging, the direction of the current is opposite to the original current direction(source current).so the current is negative. likewise the discharging voltage direction is also opposite to the source voltage direction. then why the discharging capacitor voltage in a rc circuit is positive? why it should not be negative?


texts: How is an EEPROM different from a Flash memory?

texts:
I am trying to understand the terminology used for various non-volatile memory chips for example as EEPROM and Flash.

Is there any preference to use the word EEPROM or Flash for specific type of memory chips or is it some specific technology difference in the two types?


texts: I have a board that is partially reflow soldered with a QFN and a couple of 0603 capacitors and resistors. I wanted to test functionality with this stage before I go ahead and place the other components whose working depends on this stage working right. Since adding components will mean repeating the reflow process, I was wondering if its safe to re-reflow the existing components on the board?


texts:
I am short of 1 UART in my MCU. I needed 4 but so far what I have found suitable is an MCU that has 3 UARTs in it, STM32F103. So the 4th one I will have to implement in SW.

Each of my individual UARTs are either doing RX or TX operations only. So now I have an option to implement the SW UART for ONLY RX operation or ONLY TX operation.

Which of the two should be implemented in SW, a UART which is only doing RX operation or a UART which is only doing TX operation?


texts: Why button battery LR1154 is called LR44?

texts:
It seems I cannot find complete explanation for this question everywhere on the internet.

So far, I know the followings:

L - Alkaline as +/Zinc as -
R - round
11 - battery's diameter in mm (in fact, the standard states, that the actual diameter is 11.6 mm[1])
54 - battery's height in 0.1 mm

What's the meaning of 44?


texts: Comparator resolving input voltages close to vdd

texts:
I have a design problem to solve. The problem statement goes as follows:
"Design a clocked comparator resolving input voltages close to vdd dissipating less than 100 uA".

What does "resolving input voltages close to vdd" mean? Does it mean that if the input voltage is close to vdd then the output should go to vss, depending on the reference voltage? It would be nice if you guys could explain it to me with an example.


texts: Eagle: What is the significance of the tCream layer having this "hashed" pattern?

texts:
I am trying to modify a part because in the original libary, some of the pads were of differing sizes. I would like to make all pads to be of the same size. In the following image, there are three pads. The first and third pads are in the original form.

In the middle pad, you can see that I lengthened one of the shorter pads with the polygon tool, but the polygon I get is solid.

By process of elimination (removing layers from view in the Layer Settings menu) I have found out that the these pads are in the tCream layer.

What is the meaning for the diagonal "hash" lines? Why does my polygon not have those lines, even though I'm drawing on the same layer?


texts: Choosing resistance in series with a photoresistor for best light-measurement resolution

texts:
simulate this circuit – Schematic created using CircuitLab

I have a photoresistor, R1, and as a voltage divider a fixed resistance, R2. There is a voltage of 5V over these two, and the voltage is measured over the photoresistor.

In my experiment I have a yellow LED on one side, a substance which I add blue color into, and the photoresistor on the other side. How do I decide what R2 to choose so that I can detect small changes in light (when increasing the opacity of the substance)?


texts: A mistake in "Op Amps for Everyone" about op amp attenuators

texts:
In Texas Instruments' book "Op Amps for Everyone" (5th edition, link, see page 347), in chapter 25 "Common Application Mistakes" I believe there is a mistake (ironically).
It states that it's wrong to use a unity-gain stable opamp for an attenuator like this:

I believe the statement is wrong, because that attenuator have the noise gain of \$1+\frac{R_F}{R_G}\$  which is always \$\ge 1\$. Opamp stability is determined by the noise gain (i.e. the gain with respect to the non-inverting input), not the gain of a desired signal (opamp doesn't know what the desired signal is). There is even a compensation technique which increases the noise gain preserving the signal gain (e.g. add a resistor between the opamp's inputs in fig. 25.1). Surprisingly, even in the same book in chapter 7, sect. 7.4, there is a highlighted statement, quoute:

Several things must be mentioned at this point in the analysis. First, the transfer
functions for the noninverting and inverting equations, (7.13) and (7.18), are different. For a common set of \$Z_G\$ and \$Z_F\$ values, the magnitude and polarity of the gains are
different. Second, the loop gain of both circuits, as given by Equations (7.15) and
(7.19), is identical. Therefore the stability performance of both circuits is identical
although their transfer equations are different. This makes the important point that
stability is not dependent on the circuit inputs.

It means that an inverting amp (like in fig. 25.1) has the same stability as a non-inverting amp with the same resistors (as if \$V_{IN}\$ be grounded).
Also, I sometimes see attenuators like in fig. 25.1 in real-world circuits designed by professionals. For example, in Agilent 6060B there are some examples, e.g. an inverting amp with the signal gain of \$-\frac 16\$ (the noise gain of \$1+\frac 16\ge 1\$):

Does this a real mistake in the book (survived for the 5th edition!), or I miss something?


texts: Using the logic analyser in Keil uVision5 with an stm32 nucleo F030R8

texts: as the title says, I'm attempting to use the logic analyser that is built in uVision5 with the above development board. The debugger that I am using is the on-board ST-Link Debugger. I've looked at various tutorials online and when I am on the trace tab, most options are greyed out. I select trace enable and then attempt to run the debug but I get the error "HW not present". I have seen tutorials have the trace events available to select, and this is using the same debugger (but different development board). I can get everything up and running as I like if I use simulator so it's something hardware or configuration related. Thanks.


texts: problem with Schottky Diode in motor controller circuit

texts:
I designed a simple PCB but it's not really doing what I'm looking for. It has 3 motor controllers connected to it. I want the motor controllers to be able to pull current from either the 12V lead acid battery or the power supply. When the motors stop extra voltage is sent from the motor controllers back to 12V-B and I want to make sure the diodes block that from going into the 12V-PCIE and instead the power gets dumped into the batteries.

When I turn the switching power supply off the battery is sending power back from 12V-B to 12V-PCIE and makes the fan in the power supply run. Shouldn't the diode block power from going that way? I feel like I'm missing something really simple.

The blue is the ground plane. In the top of the board are the two 12V planes separated by the diode.


texts: Galvanic isolation - threshold for considering a voltage to be dangerous

texts:
I have been wrestling with the philosophy behind galvanic isolation, and whether or not it makes sense to employ it in an application I am working on.

I understand galvanic isolation is required for wired communications between two circuits operating at different ground references (floating w.r.t. one another).  The need for galvanic isolation in this case is self-explanatory (comms won't work, stuff gets fried, etc).

I also understand that the concept behind galvanic isolation for safety is to eliminate the conductive path between a power source and a point in the circuit that the user might touch (e.g. a jack or other wire-to-board connector).  In this case, if there is a problem with a circuit that the user touches, no current will flow through the user to earth ground.

My question is this:

At what DC and AC voltages is galvanic isolation required from a safety perspective?

For example, if I want to measure AC and DC signals, at what point do I need to isolate the ADC section of my board from the section that supports user interface peripherals (see below diagram)?

In other words, how big does V1 or V2 have to be before I need galvanic isolation between the ADC section and the rest of the board?

simulate this circuit – Schematic created using CircuitLab


texts: Calculating base current without knowing current amplification

texts:
So I'm currently doing an assignment where I'm meant to design my own common emitter. I'm supposed to choose the Q-point of my collector current and choose my own signal amplification (Av). During this design, I'm assuming (I_C=I_E, if I_B << I_C) and (I_R1=I_R2, if I_B << I_R1)
I'm using the hybrid-pi model.
I got the following value:

Vcc = 22V
Voltage over R_C: 11V
Collector resistance: 3.7k ohm
I_CQ (Q-point of collector): 3mA
Small signal amp: Av = 6 times.
Emitter resistance: R_E = -(R_C/|Av|) = 615 ohm
Voltage across emitter resistance V_Re: 1.85V
Voltage at base V_B = Vbe + V_Re = 0.7 + 1.85 = 2.55V
I_R1 = I_R2 = I_C/10 = 3mA/10 = 0.3mA
V_R2 = 2.55V (Same as V_B)
R_2 = 8.5k ohm
V_R1 = 19.45V
R_1 = 65k ohm
My voltage (V_CE) across the transistor is 9.15 V

When I'm going over to small-signal analysis, to calculate R_in and R_out. I need to know the base current I_b or current amplification beta/hfe, however, I know neither with makes me get stuck.

r_pi = beta/gm

Circuit diagram in LTSpice


texts:
I am using isolated RS485 for communication. MCU & RS485 IC communication is through UART. IC supports 500kbps datarate
Configuration
a) Baud rate- 460800
b) Every 0.1s I am sending 288bits data from tool to board (RX), initially it work fines after sometimes my boards hangs
Is this because the RX is getting full & it hangs the board or is it related to hardware.
same configuration if I increase the time interval to 1s, it works fine without any issue.
Please help me to solve the above issue, it would be grateful for your suggestion.


texts: Im working on a Visible light communication project. Its a simplex transmitter receiver setup using an LED to send data to a photodiode receiver. Im thinking of ways to encode the data for transmission and was wondering how exactly i would implement a Frequency Modulation setup. I know the basic concept of FM but dont understand how the receiver perceives these shifts in frequency(wouldnt it take a few cycles of high/low to even calculate frequency, and if so wouldnt this be a limit to max bitrate). Ill be using an arduino board to interpret the received signal. How would I go about using FM to send data from an LED to a receiver and decodw that information?


texts:
I have to design a electronics device that is specified for environmental operating conditions of 0°C to 60°C with 5% to 95% relative humidity (non condensing).
I think the temperature part should be covered with commercial component selection (0°-70° operating temp.), but what about the humidity requirement?

Is this humidity specification hard to achieve?
Do I need to protect the PCBA with conformal coating?
What are the general recommendations for different humidity specifications?

Of course I will need to perform some tests in the climate chamber. But I think there should exist some general guidelines for the design regarding humidity?


texts:
I'm would like to make a connection between a ESP32 and a Allwinner A20 CPU in which the ESP32 would provide the Wifi/Bluetooth connectivity for the rest of the system.

They both mention i2c, spi and SDIO in their datasheets.

Which one of those would be considered the a best practice?
Are the additional protocols that could be taken into account?


texts: Is it a good PCB design practise to choose components with the same footprint?

texts: Most of the components I have selected for my project have 2012(mm) footprint while some others have 1608, 3225 and 6432. Does it matter that some components have a different footprint? What is a good design practise?


texts:
From an old dust buster I've got this electro motor, the included battery pack and the charger:

I ripped everything apart (the dust buster was broken) and the motor still works. After playing around with it for a while and letting it lying around for about two weeks it suddenly revs a lot slower. I supposed the battery pack was drained so I hooked up the battery pack to the charger and let it charge for a night. Unfortunately the motor still turns very slow.

Since I want to use this motor for my first home robotics project (making a kite fly with my computer), off I went to the local electronics store where they measured the charger to give 16V (even though it says 21V) and the battery pack to give about 5V. I then hooked up the motor directly to the charger, but unfortunately it doesn't even move an inch then.

So now I wonder:

Why doesn't the motor spin at all when hooking it up to the charger? (Could that be because the 250mA is too low?)
Why doesn't the battery pack charge at all? (this bothers me the most!)

All tips are welcome!

[EDIT] Just some more info on the batteries: there are ten 1.2V and 1700mAh batteries, which makes it a 12V battery pack. The question arising from this:

Can it be that the battery pack is not charging because it is a 21V charger on a 12V battery pack? Do I need to put a resistor in between? And if so; what kind of resistor?


texts:
For a few years, I have been using microcontrollers to do simple hobby projects that require using various communication protocols (serial, i2c) and toggling GPIO pins.  However, the computational capacity of microcontrollers is no longer sufficient for the projects I want to do.  Hence, I am looking for (if it exists) some kind of USB peripheral that has external pins similar to an Arduino's (e.g. PWM, rx/tx, I2C, etc.), but which can be controlled directly from a script running on my desktop or laptop.  In other words, I just want to use it as an interface between a PC and other electronic devices.  Do such things exist, and if so, what are they called?  Ideally, I would like to be able to control the hypothetical device with Python (perhaps using pyserial).  An absolute requirement in what I am looking for is the ability to communicate with Dynamixel motors, which use half-duplex TTL.

Thanks in advance for suggestions!


texts: TXB0102 only translating in one direction

texts:
First time using the TXB0102 and I can only get it translating in one direction.  I'm using it to interface a 5V ATMEGA2560 hardware UART port to a 3.3V device with VOH 2.4-3.1V (TXB0102 table says VCCI x 0.65 so is well within spec) and VIH 2.0-3.6V.
I have VCCA @ 3.3V and VCCB @ 5V with OE controlled by an IO on VCCB and can get data from 5V>3V but not the other direction.  Screenshots are taken on matching A/B pins.  Any ideas?


texts: Power switch between two sources using mosfets

texts:
A new problem I have is to create an automatic switch between two sources, only one of the sources should be active at a time. There is a "backup" source (5V battery), as well as another source. Once this source drops below a 3V threshold it should stop (and go back to the battery).

We wish to use a power (N- type)mosfets (with a \$V_{gs-th}\$ of 2V) to do the switching. The best circuitry that goes into the direction I've come up to is as following:

simulate this circuit – Schematic created using CircuitLab

(Notice the diode above the mosfet is to emulate a power mosfet)

Now the gate voltage is simply the \$\frac{2}{3} \cdot \left(V_{bat} - V_{var}\right)\$. (PS: I know this 2/3rd is not correct, it is currently included in the schematic so I have a point where I can edit the exact voltage difference)

Now this works for the battery: it is disabled as long as the variable source is above the threshold. However this isn't the case for when the variable source becomes too low. Then the variable source should be "disconnected" (so it can charge up again).

But I can't seem to add such a feature without breaking the current way.


texts:
In a previous question, it was brought to me that LEDs do not obey the Ohm's law.
(See Calculate expected voltage around a resistor)

Simply put: how is that?

What makes them behave so differently? How should we treat them in a circuit and calculations?

Are there other components with similar behavior?


texts: HP 1740 monitor stay on 2-3 seconds, turn off and repeat

texts:
I have an HP 1740 monitor that, when I turn it on, just remains 2-3 seconds to display and turns off completely (even the pilot). It seems to me that the problem is not in the backlight. I opened the monitor and on the power supply board, I didn't find anything visually damaged.

I measured all the capacitors with a multimeter (on the PCB, I did not desolder them) and yet only the two large green capacitors rated 150 with the multimeter in Diode mode.

I also tested the MOSFETs (without desoldering) between the drain as positive and source as negative. In all, the value of Diode mode went up.

I suspect the 1200AP60 integrated circuit, but I don't know how to test it. Could it be the problem?

I am an enthusiast, trying to learn more about electronics and how to solve.


texts:
I have been using and making LED flashlights for years now and I am VERY familiar with all of the circuitry and technology inside of them, but I just got my first LED house light bulb that runs off of 110v AC electricity.  It is very similar to a flashlight - it has a large heatsink, and 1 or more LEDs inside of it (brand and specs of emitters, I do not know).  The part that I am most curious about is how the electricity from the socket gets to the emitter.  In a flashlight the power comes from a DC battery through a current regulator (LED driver) and into the LED itself.  This is not difficult because the voltage of common LED emitters is about the same voltage as Lithium batteries (3.7v, 7.4v, etc) which makes the current limiting relatively simple coming from a one or two cell light.

How does this work for a high voltage AC bulb?  Is there a transformer and rectifier inside of EVERY bulb (I sure hope not), or are the emitters manufactured to run off of 110v AC power and just use half of the wave cycle?


texts: Difference between multi layer chip inductor and high frequency chip inductor

texts:
What is the difference between a multi-layer chip inductor and a high-frequency chip inductor?
And also what is the difference between rated current and saturation current if an inductor?


texts: PIC12F683 or PIC16F688 assembly or C blinking LED example with XC8 compiler, MPASM or gputils

texts:
Hello I am new to PIC programming and I finally have got my dev environment working, I downloaded the XC8 compiler from microchip and also as backup I downloaded the gputils assembler. I have not been able to get anything compiled/running and I would appreciate an example. If someone could write a small program demonstrating how to set the config bits and the crystal frequency in either assembly to assemcle it with MPASM or gputils or C to compile with XC8 I would appreciate it. I have a PIC12F683 and a PIC16F688 although for this example I dont think much platform specific stuff maters. Anyways I gave it a shot and here is what I got, but it is not working. Thank you

#pragma config FOSC = INTOSCCLK // Oscillator Selection bits (INTOSC oscillator:

CLKOUT function on RA4/OSC2/CLKOUT pin, I/O function on RA5/OSC1/CLKIN)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = OFF      // MCLR Pin Function Select bit (MCLR pin function is digital input, MCLR internally tied to VDD)
#pragma config CP = OFF         // Code Protection bit (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Code Protection bit (Data memory code protection is disabled)
#pragma config BOREN = OFF      // Brown Out Detect (BOR disabled)
#pragma config IESO = OFF       // Internal External Switchover bit (Internal External Switchover mode is disabled)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enabled bit (Fail-Safe Clock Monitor is disabled)

#define _XTAL_FREQ 8000000
//INCLUDES
#include <xc.h>
#include <stdio.h>
#include <stdlib.h>

void main(void) {
 GPIO = 0x00;
 ANSEL = 0x00;
 TRISIO = 0x00;
 ADCON0 = 0x00;
 CMCON0 = 7;
    while(1)
    {
        GP0 = 1;
//dont know which delay function to use
        GP0 = 0;

    }


texts:
Yes, this is a problem given in class. I'm studying for a test and coudn't find an expression to (). For me it seems like there is not enough data to do that. Can someone give me a direction?

A power supply V1 is connected to a load ZL by a wire of impedance 6,4 + j4,8 Ω, as shown in the following picture. Knowing that the angular frequency of the supply is 200 rad/s, the voltage on the load is 100 V (rms) and that it absorves 1000 W with a power factor of 0.8, determine:

(a) The voltage expression for the power supply ();


texts: Will a flyback diode prevent an analog MCU input from being destroyed in this schematic?

texts:
Quick question: In this schematic, would D1 prevent high flyback voltages caused by the motor going into the voltage divider network and destroying pin A0 on the MCU? Pin A0 can only tolerate 5V max. If not, what would be a better way to do this circuit? If it's not clear, I'm using Pin A0 to measure the battery's voltage.

Thank you.


texts: An overhead of running program on Linux vs embedded bare-metal

texts:
Let's say I have some multi-core ARM Cortex-A.

Now I have there a Linux, with RT_PREEMPT patch (so called real-time Linux). I run a processes with affinity set to one core and high priority (above 50).

Thanks to real-time patch, even the kernel scheduler cannot preempt my process, and thanks to affinity it can run all the time on a single core (and OS on others).

In such conditions, is there any difference (i.e. overhead) of running such code on Linux vs bare-metal?
Will the performance be the same? If not, why?


texts: Clipper circuits, voltage across voltage divider

texts:
I understand that using diodes we can control the range of voltages across a voltage divider. However, following this tutorial I noticed he drew a smooth linear transition for voltages 0-6.7 in the bottom right corner.

I would've thought that once the ideal diode reaches its forward bias voltage and connecting the voltage source, the voltage across resistor R_L would immediately be 6.7V because it is in parallel like so:

Can someone please clear this up for me?


texts: How do capacitors help in smoothing potential difference from a full wave bridge rectifier?

texts:
Let me establish some facts I have understood by myself: The polarity of resistor does not change, as the current from A.C source flowing through does not change direction. The D.C potential difference value fluctuates from zero to maximum. To reduce this fluctuation a smoothing capacitor is used.

What I don't understand is:

Is the equation \$t=RC\$ applicable to both charging and discharging of capacitor?
Is the time constant the same in both cases?
If so then why does the capacitor charge fully in time \$t\$ as the potential difference rises to maximum initially but discharge slowly as the potential difference falls? Its time constant for charging and discharging is different apparently! It's greater for discharging and less for charging. Why is this?
Initially, as the capacitor charges won't it cause some of the current to be diverted towards itself and less current would flow through resistor, as they are arranged in parallel?


texts: In practice, is there a limit to the insulating properties of a transistor acting as switch?

texts: I would like to know if there a limit to the insulating properties of a transistor acting as switch?


texts: Wire microswitch so state can be read from Raspberry gpio

texts:
I'm trying to check whether a series of valves (described here Can I measure if current is on or off in cable with 24v DC (in a cheap way)) are open or not.

Updated question to be more specific after getting some answers:

If I mount a micro switch, like the one in the image below, on the valve so that the "normally open" pin on the switch is closed when the valve is opened, how would I wire it to a gpio on a Raspberry so I can check if it closed or not, e.g. every 10 minutes?

I might use the gpio utility to check the pin. Would I then wire the "common" to a 3.3v on the Raspberry and the "normally open" to a gpio and then set the pin's mode to pulldown with gpio mode <pin> down? And the read the pin with gpio read <pin>?

Question 2: Can I wire multiple switches to the same voltage pin on the Rapsberry?

Question 3: Can I freely select to use either 3.3v and 5v?


texts:
Power calculation for stepper motor with 1.2 Ampers and 4 volts.
Is P = V * I enough for this? If not, should I do a separate operation with torque?


texts:
I'm studying this protection circuit that protects a microcontroller from inductive transients, switches, and other things in a small aircraft, which would be similar to a car/motorcycle/boat in that it has to deal with relays, contactors, the alternator, and other inductive things.
I understand the purpose of Q3/D5/R5 as the reverse polarity protection.  I understand the filtering caps (C8/C7/C5/C6) around the voltage regulator.  But I don't understand the purpose of D4, C9, and D2.  Thus my question:

What does D2 do?  Looks like a TVS diode, is that to short out the input when it's well over voltage?

What does C9 do?  It appears to me the R5 limits the current and biases Q3, but why the cap?  Looks like an RC circuit, but why would we need a filter here?

What does D4 do?  I can't think of a case where current would ever flow from the input pin of the regulator and I've never seen a diode like that next to a regulator.

What would be a typical part for Q3 and D2 if I desired input protection to +/-60V but typical input voltage of 14.5?  Looks like I have a bit of reading to do in regards to FET selection.

Thanks.


texts:
I designed a small board that needed the capability of communicating over USART, so I threw in an FT230XS USB|USART Bridge. The device use is so simple that I am out of ideas for troubleshooting.

Looking over the datasheet we can find a suggested bus-powered configuration

I placed the device on my board exactly as they have don here, minus some of the bus filtering

I have measured connectivity between the USB side and the 27R resistor, as well as the FT230Xs side and the 27R resistor. I also get all the expected voltages around the device, including the 3.3V output shown in the diagram below. Everything is as expected, it's just that nothing actually happens when I plug the device into a usb port.

I have tried plugging the device into both a Win8 machine and a linux box, but nothing happens. Both machines have the appropriate drivers installed to my knowledge.

The interesting thing here, though, is that no only do the devices not attempt enumeration with the usb stack of the host machine, but they do not do anything. I put a scope on either side of the 27R resistor and no data appears to be going through. Namely, the FTDI chip is not attempting to identify itself on powerup, so the host machine obviously is not aware of anything having been hot-plugged.

Is there anything immediately wrong with the design? Are there some additional steps to getting the FT chips to work? After the first FT chip would not enumerate I figured I may have damaged it at some point. Since I ordered three it was no big deal. I used my heat gun to remove the first and solder the second. Again, the second chip demonstrated the same behavior (or lack there of). I then went on to change out the chip a third time, but once again nothing is working.


texts: Emf interference on arduino and breadboard , using 74HC595 shift register, how to prevent it?

texts:
I’m using a 74HC595 chip (shift register) NPX semiconductors, connected to and arduino board. Basically the shift register switches on and off 8 leds in sequence.

Everything seem to be working, code and pin wiring to the chip are fine.

The issue is that sometimes the circuit seems to have some problems and the leds are all frozen. I've noticed that when I move the breadboard in some specific locations or simply pass the hand over some wires all the circuit starts working fine. Clearly I’ve checked all the wiring connections and from that point there is no problem. What I’m suspecting is that there is some kind of EMF noise disturbing the setup.

From what I know only high frequency application can be affected by this problem, but I’m working with just 5V and nothing is going beyond 1MHz.

What can be the possible issues? What are the topics I need to study to prevent this problem? How to prevent it?

The following are links to:
My video showing the possible noise problem
The schematics I got from fritzing.org

http://youtu.be/VOEzuPjwXAw
http://fritzing.org/projects/shift-register-74hc595

I've added a 100uF capacitor, but nothing solved


texts:
ATMEL

MARKINGS: 58BL W 9H0336E

I have no idea what these marking indicate, can anyone here help me ID this part?


texts: Nicomimi sensor not sending any values to bluetooth

texts:
I am trying to replicate this project.

TL;DR for the project:

Hack the nicomimi toy to get the chip to send signal to HC-05 bluetooth.
connect a PC to a arduino leaonardo which in turn is connected to a HC-06 which receives the bluetooth signals sent by HC-05.
Based on the signals received program the leonardo to press the corresponding keys in the keyboard.

I did it as per the instructions and ran into a problem. I am always getting a single value in HC-06. I suspected that it might be a problem with the connection established between HC 05 to 06. So  I eliminated the middle man and directly connected the Tx pin from the nicomimi headset to the leonardo and printed whatever value the device was sending. It appears so that it is always sending a static value.

Is there a way to check if the nicomimi chip is working correctly or not. or is there any error in the circuit I have made?


texts:
I have some custom components built. Some of the components are showing as off-grid in schematic. I am attaching the screenshot of the component designer and schematic designer. Can someone please tell me how this can be fixed?

This is the component

This is the schematic. Few pins are off-grid.


texts: How does a fuse resistance vary with temperature change?

texts:
In datasheets usually a cold resistance is given, which represents fuse resistance at low load, according to Littelfuse guide https://m.littelfuse.com/~/media/electronics/product_catalogs/littelfuse_fuseology_selection_guide.pdf.pdf
I am trying to figure out what would a "hot" resistance of the fuse be - resistance at rated current and stabilized voltage drop. Is it safe to assume it should be higher than cold resistance, and is there a rule of thumb that can help with its estimatation?


texts: Understand datasheet current transformer

texts:
I am trying to understand the datasheet of a small transformer (SMT transformer, ref B82801B from EPCOS, available for example here: https://www.elfadistrelec.no/Web/Downloads/_t/ds/B82801B_eng_tds.pdf?mime=application%2Fpdf ).

I am not an electrical engineer, and here is my understanding of how a transformer works (I write this here as it influences how I read the datasheet). There is a primary, resistance \$R_1\$ and inductance \$L_1\$, and a secondary, resistance \$R_2\$ and inductance \$L_2\$. Considering perfect coupling between those, the coupling coefficient is M = \$ \sqrt{L_1 L_2} \$. Therefore, I expect that the transformer follows equations (with \$V\$ and \$I\$ tension and intensity, and index indicates primary / secondary):

\$ V_1 = R_1 I_1 + L_1 \frac{d I_1}{dt} + M \frac{d I_2}{dt}\$,

and symmetric formula for \$V_2\$ (the sign before M may vary, depending on how the transformer is wired).

When I look in the datasheet page 3, I get to know which pins are to the primary and secondary coils. This is great, I think I get it right.

When I look at the datasheet page 5, I get:

The turn ratio. This is great, I understand (it will give me amplification if no load).
The typical max DC resistance \$R_i\$ for the primary and secondary. This is great, and I get the right value when I measure with the multimeter.
A \$L_{min}\$ value. What is that? Is it \$L_1\$, \$L_2\$, or \$M\$? Comparing the scaling of \$L_{min}\$ with the number of turns in the secondary, it looks like \$L_{min} \propto N_2^2\$, so I would guess actually \$L_{min}\ = L_2\$ as in general for a coil, \$L \propto N^2\$. Am I right?
What is Voltage-Time product? I guess it is maximum value of (Voltage) * (time when applied), am I right?
Why is there a recommended \$R_T\$?


texts: value of resistor when converting HC outputs to non-compatible inputs

texts:
Here's what I'm trying to do.

I have a 32K EEPROM (IC1 is an AT28C256) with data burned onto it.

What I want to do is select the address I want using shift registers and then load the output value (code) into the LCD.  The "TRIG" (or E) of the LCD is connected to a monostable output (not shown). It is setup so that if no activity occurs on the clock input for a certain time then the address is valid and E changes state.

In the past I tried my setup without pull-up resistors and it failed (with some output pins of the 74HC164 reporting lower voltages than normal).

I feel my options are:

Change 74HC164 to 74HCT164

or

Use pull-up resistors

If I use the first option, the availability of the chip is lower, and wouldn't the chance of emi go up?

I tried the second option with 10K sip resistors, but for some reason I think that value might be too low.

What I think is best is to make the sip resistors values higher, but what's the highest I can go before the outputs don't register properly?

or am I really better off replacing 74HC with 74HCT?


texts: Has there been any deliberate implementation of combinational logic soft error correction in any consumer-level product, like a CPU/microcontroller?

texts:
Prologue
It is well known that many error detection, mitigation, and correction methods, such as parity or ECC, have been available in large memory banks, like for RAM, for decades now, and even in CPU caches and sometimes parts of state machines.
These are mostly large implementations of sequential logic where single event upsets from cosmic rays have a significant enough chance of causing a lasting bit flip, due to the smaller feature size, density, number of latches, etc.
Throughout most of computer history, the combinational logic of the CPU, or small sequential logic like singular latches or registers, have remained unprotected. This is mostly due to the unintentional electrical, logical, and temporal masking effects that are due to the low transistor count, number of logic gates, size of transistors, etc., which has made combinational logic soft errors due to SEUs mostly negligible.
Over the past few years, the reduced feature size has become a large concern because it may be making combinational logic errors common enough to be a real problem.
Question
Thus, I was wondering if there have been any significant implementations of soft error mitigation or correction in combinational logic circuits or single latches/registers in any consumer-level product, like a CPU or microcontroller.


texts:
I have procured some supercaps.
No datasheet was provided. The only data I have is what is printed on the caps themselves: "4.0F 5.5V cda®"

Since my DMMs don't measure capacitance in Farads, I setup the following circuit shown below. Two "10Ω 1% 2W" (20.2Ω and 20.3Ω measured) caps in series with the cap.

simulate this circuit – Schematic created using CircuitLab

Note that I did not actually use a switch, I simply connected a banana plug. I did that to avoid extra variables (switch resistance and power rating, as well as power supply startup time).

That being said, with a large expected time period of 80+ seconds, I figured that using a stopwatch and monitoring my DMM would suffice.

The RC time constant is: R*C = (20.3Ω)*(4) = 80.2 seconds

Which I take to mean that if I apply 5V as shown in the circuit and close SW1, the cap should reach 5V * 0.632 = 3.16V at 80.2 seconds. The current limit on the supply was set to 2A (more than enough).

The cap went from 0V to 3.16V in approximately 38 seconds, at which point I removed the cap from the circuit.

Solving for capacity: C = (38 seconds)/(20.3Ω) = 1.87 F, only 47% of the 4F labeled!

About a minute after being removed from the circuit, the voltage on the cap had stabilized at about 1.28V. Should I be using this value instead? That would suggest 6.43F, so I'm guessing "No".

I then tried the same test with another cap of the same specs... same result.

I next tried a discharge test, going from 4.8V to 1.64V. That should have taken 87 seconds, but instead took only 28 seconds, hinting at a capacity of only 1.27F.

However, by leaving the cap to discharge for 55 seconds showed 1.1V, suggesting a capacity of 1.82F. That's odd to me because it means that it's not following the predicted curve. And that would mean that I will end up calculating a different capacity depending on the time I record at. But that shouldn't be.

The following image is from hyperphysics.phy-astr.gsu.edu:

I'm wondering what margin of error I should expect from a test like this. Assuming my multimeter is calibrated beyond practically needed, and that recorded times are valid, is it possible that the capacitance is closer to 4F?


texts: A/D 10 bits in Silicon Laboratories C8051Fxxx ,interrupt

texts:
I am reading code in C to convert analog to digital and didn't understand this part. I didn't post the whole code but this is enough to understand the point of my questions since my questions are a bit general.

void ad_isr (void) interrupt 10     /*I didnt understand when does the program calls the interrupt and why do we need an interrupt?*/
{
    lowbytevoltage = ADC0L;     highbytevoltage = ADC0H;
    voltage = highbytevoltage*256 + lowbytevoltage;
    array [b] =voltage;

        if (b == 31)
        {
            for (c=0; c!=32; c++)
            {
                Voltage = Voltage + array[c];
            }
                voltage = voltage/32;

Why do we need to sum 32 consecutive voltages and then divide by 32?
Also I saw in an example code from the internet

for(i=0;i<16;i++)
{
    ConvertADC();
    while(BusyADC());
    ADCResult += (unsigned int) ReadADC();
}
ADCResult /= 16;

So I thought they may have something with each other since 32 is the double of 16


texts: Mechanism of conversion of electrical energy to EM energy in LEDs

texts:
I've always been intrigued that electrical energy can just disappear out of a circuit 'into the aether' as RF.
Of course thinking about it, some energy 'vanishes' as EM radiation even in a filament lamp or infra-red bar heater but not that much.
Recently, with LED efficiencies in the order of ~30%, it's interesting to think that for every 10W or so dissipated in LEDs, only say 7W or so needs to be considered as heat !
Question: I'm familiar with the photoelectric effect in solar panels etc but is the light emission mechanism in LEDs related to this or somewhat different ?


texts: Risks of riding E-bike under high voltage power lines

texts:
I've recently experienced a small electric shock each time while I was passing under international power lines for 3 times. They transport at around 330K volts.
While it didn't hit me really hard, a few questions came to my mind:

Is there any influence of the battery or motor on power level of such shock? If so, how specs affect it.
What is the influence of the weather conditions (fog, rain) in this case.
How serious it can get with lower altitude to the lines (on mountain terrain etc) and higher voltage (400-500 kV).


texts: Advantages and disadvantages of reading a current-sense amplifier with different gains on I2C

texts:
I am writing an I2C wrapper for the MAX9611 chip. For the current-sense amplifier (CSA), according to the datasheet there are 3 selectable gains (1x, 4x and 8x):

When I read the 12bit ADC registers for all 3 gains, I get the same raw values. But to convert it to real current I have to multiply them with some constants which are different for each gain, e.g. for 1x it is 1.075 and for 4x/8x constants are 0.269 and 0.134. I have found these constants on some sample codes and I have no idea how they are calculated but I have found this table in datasheet but I can't make sure why:

So my guess is, when I select the gain=8x, the resolution (or accuracy?) of my reading is much higher compared with gain=1x but what will I lose in doing so?

So my question is, what are the advantages and disadvantages for reading from lower or higher gains? Also, what should be the correct multipliers if I want to convert raw ADC to real current? (the ADC is 12bit) I power the chip from a 3.3V source.


texts:
I am confused with the working of an sr latch.

simulate this circuit – Schematic created using CircuitLab

The two inputs provided to nand1 is S and q2 and the inputs provided to nand2 is r and q1. q1 is the output of nand1 and q2 is the output of nand 2. When s=0 and r=1, according to what my book says, nand1 will have 0 and 'x' as an input(where x can be any bit 0 or 1 as it doesn't matter because anything NANDed with 0 results in a 1). So the result q1 is 1 which is fed to nand2 along with r=1 to give q2=0. Now here is where I am getting confused- Initially if we assume that we have just constructed this latch. Then obviously both q1 and q2 will be zero since nothing has been commenced. Since both the bits s and r come at the same time, so when s goes to nand1 then at the same precise time r goes to nand2. Now if we take the above values again, i.e(s=0,r=1), nand1 is provided with s=0 and q2=0 which results in q1=1. And nand2 at the same time is provided with r=1 and q1=0 that results in q2=1. This results in the unwanted stage where both outputs are 1.


texts:
I wrote a program for a '11' sequence detector to be implemented by both Moore and Mealy machine. The problem statement is for z to be asserted high after x has been high for 2 cycles. I've attached my implementation below, but what I am seeing is that for both FSMs, z is asserted one cycle too early. Can anyone spot the error in my FSM or code? I would really appreciate any input on what I may be doing wrong! Thanks

FSM:

Systemverilog code:
Moore:

module moore_fsm
(input bit clk, reset, x,
  output bit z);

  typedef enum bit [1:0] {A, B, C} states;
  states current_state, next_state;

  always_ff @(posedge clk, negedge reset) begin
  if (~reset)
  current_state <= A;
  else current_state <= next_state;
  end

  always_comb begin
  case (current_state)
  A:begin
        z=0;
        if (x==0) begin
      next_state = A;
        end
        else begin
        next_state = B;
        end
        end
  B:  begin
        z=0;
        if (x==1) begin
        next_state = C;
        end
        else begin
        next_state = A;
        end
        end
  C: begin
      z=1;
     if (x==1) begin
      next_state = C;
      end
      else begin
     next_state = A;
      end
      end
  endcase
  end

  endmodule:moore_fsm

Mealy:

module mealy_fsm
(input bit clk, reset, x,
  output bit z);

   typedef enum bit {A, B} states;
    states current_state, next_state;

  always_ff @(posedge clk, negedge reset) begin
  if (~reset)
  current_state <= A;
  else current_state <= next_state;
  end

  always_comb
  begin
  case (current_state)
  A: if (x==1) begin
      next_state = B;
        z=0;
        end
        else begin
        next_state = A;
        z=0;
        end
    B: if (x==1) begin
        next_state = B;
        z=1;
        end
        else begin
        next_state = A;
        z=0;
        end
  endcase
  end

endmodule:mealy_fsm

Testbench

module moore_mealy ();

bit clk, reset, x, moore_z, mealy_z;

moore_fsm dut1 (clk, reset, x, moore_z);
mealy_fsm dut2 (clk, reset, x, mealy_z);

initial begin
reset = 1;
 #1 reset = 0;
 #1 reset = 1;
 #5 x=0;
 #5 x=1;
 #28 x=0;
 #20 x=1;
 #10 x=0;
 #10 x=1;
 #150 $finish;
end

always begin
 #5 clk = ~clk;
end

endmodule:moore_mealy

Output Waveform:


texts: Why don't switches appear in circuit diagrams of DC motors?

texts:
DC motors are typically represented in circuit diagrams as follows,

This sort of diagram seems to show up in controls and system dynamics courses.

Most common DC motors have commutators, switches that change the direction of current in the armature coils. Without a commutator, a DC coil would just act like an electromagnet and align with the stator field. With a commutator, the induced magnetic field changes direction, twice per revolution. The faster the rotor turns, the faster the current in the inductor should change direction. This switch never shows up in the textbook diagrams I see. What gives?

Is the inductor in this diagram the actual coils of wire in the armature, or does it represent an effective inductance that is averaged out over time? Also, is back voltage constant at a constant angular velocity, or does it, too, switch on and off? Is all of this a pious lie disseminated by controls professors?


texts: Contradictory Vce values in transistor datasheet

texts:
So I'm a hobbyist mostly working with micro-controllers and simple low voltage digital circuits and I always thought the TIP120 transistor is a useless one for me because it has a Vce(sat) of around 2V. But yesterday I was testing it in a circuit and I realized that the Vce is actually way below that. So I got curious and read the datasheet again thinking maybe I had made a mistake and then I realized that Vce values are contradictory in it.
In the Electrical Characteristics table it states that Vce(sat) @ Ic=3A, Ib=12mA is 2 Volts (in the Max. column):

But further down in the Typical Performance Characteristics section you are presented this:

Here even the hfe is the same so at 3 Amps you have the same 12mA of base current that was specified in the table. But as you can see Vce is 1V here as opposed to the 2V stated in the table. And at 5 Amps it's ~1.3V as opposed to 4V(!) stated in the table.
So what's going on here exactly? 4V compared to 1.3V is a lot of difference. Is it because the table is stating the maximum? If so, what factor can cause Vce to change so much given that Ib and hfe are the same?


texts: GPS and Communication (802.11, BT, GSM/GPRS, etc.) ICs

texts:
I'm trying to do the preliminary proposals for a small, low power, low cost unit that is capable of reporting it's location to a central service.  These devices will generally be in a small urban area, but locating them outside that area (i.e. for loss prevention) would be a big bonus.  The run will be somewhere around 500 units, so [small] bulk pricing of components can come into play.

I'm expecting to use a standard 16 or 32 bit PIC microcontroller, along with a GPS chip.  The part I'm stuck on is communication.  I've come up with a few ideas:

Wifi - Expensive, but excellent coverage in my target area and decent coverage outside it, simplest integration on the back end
Bluetooth - Cheaper, but intermittent coverage in my target area and zero coverage outside it, more expensive to integrate on the back end
2 Way Pager - Cost ???, can't find any information (I don't even know the name for this kind of device), probably not too hard to integrate on the back end (especially if the carrier supports emails)
GSM/GPRS/??? - No idea, just throwing it out there.
Other ideas?

Does anyone have recommendations for the GPS and comm units?

Requirements:

First and foremost, this needs to be geeky and cool.  Frankly, that's the #1 criteria that will sell this
Second I need to have a relatively accurate fix on-campus (about 20M ft^2).  Let's say within 50 feet
Power consumption and cost both need to be low.  Like, able to run for 24 hours on 2 AAs, and the entire unit for under $50.  I can dial down the reporting rate to once every half hour to achieve that battery life, though once every ten minutes is ideal
Lowest consideration is the potential to be able to find the device if it is stolen.  This isn't a hard requirement, but if it's possible, all the better.


texts:
I  was looking into the polarization of patch antennas (for GNSS use).
I found this website (http://kempbros.github.io/antennas/Patch_Antenna_Generator/) which gives the geometry of the antenna starting from a couple of parameters (frequency, dielectric constant, etc..).
From what I can see the polarization of the antenna (LHCP or RHCP) is determined by little cuts of the corners of the patch.

I found interesting that such a little change has such an impact on the characteristic of the antenna.
Is there an intuitive explanation for this? (I do not have any antenna theory background)
Polarization of Patch antenna - Intuitive explanation


texts:
Are there other options for a small (< 5mm long) low-g motion sensor than accelerometers? I don't need to measure the acceleration picking up my device causes, I just want a 1/0 signal when it happens. Preferably very low power, <10µA would be nice.
(IIRC I once saw a purely mechanical small sensor mentioned in an answer here, but I can't find it anymore. Purely mechanical means zero-power.)


texts: Half Bridge Inverter Effect of Load on waveforms

texts:
I have made a half bridge inverter, in the lab and on simulation software. I have used the gate drive IR2110a and am supplying it with a square wave pulse and it is then applying the gate voltage to the high and low side MOSFETs (ho and lo on the diagram).

I have found that using a purely inductive load of 100uH causes the circuit to not work as expected, as the Vs (which should be a square wave) massively droops and therefore the Vho is too small to turn on the high side MOSFET for the normal time expected. Shown below:

Increasing the value of the inductance reduces this droop but there are still sloping tops on the Vs waveforms. The current in the inductor, I(L1), also becomes the expected triangular wave rather than the more curved wave found above.

Can anyone explain in terms of what is happening in the circuit why the droop happens? and also why the current in the inductor looks as it does in the first set of graphs?


texts: Writing data into previously unwritten addresses in W25X10CL spi data flash

texts:
I am using a W25X10CL spi data flash to store data.

Following is the data sheet for the data flash:-

https://www.winbond.com/resource-files/w25x10cl_revg%20021714.pdf

I need to read data from multiple sensors every one hour and store them in the data flash till i get a request to read back this data.

Once i get a request to read the data, i need to fetch it from the data flash and transfer it.

I had some questions which i was not able to find in the data sheet.

I am aware that:-

The mentioned data flash allows only sector/block/chip erase
I need to erase the address locations before writing any new data
Data cannot be overwritten at the same address locations

My questions are:

Can i write data to different addresses in the same page (where data was not written previously)?
Can i keep appending the data into the data flash?
Is there a way to erase only certain addresses instead of doing sector erase?


texts: Measuring Input Impedance of Transistor with LTSpice

texts:
How do you measure the input impedance of a transistor with LTSpice?

Consider the following circuit:

The above just biases a transistor so that the collector is 1/2 the supply. I used a current source with 1A AC. I then plotted the voltage at the base divided by the current at the base because we all know R = V/I.

So from this plot it looks like it's about 2.9K. Is this correct?

Although the impedance depends on the bias. Obviously with the bias high enough the impedance of the transistor is 0 - it's just a diode. Right?


texts: What is the difference between Microchip and ICD and PICKit?

texts:
I understand that Microchip has In-Circuit debuggers (ICD) which gives insight into a running PIC (or dsPIC for that matter) in real time. Then we have the ICE which goes a step ahead by replacing the microcontroller within the board and emulate it. The ICE gives full view of what would be happening inside the PIC had there been a real microcontroller on that board there.

Microchip also has something called the PICKit. It can be used to program a PIC. Can it also be used to replace the ICD? I am specifically referring to PICKit 3.

For Easy PIC PRO v7 here is a section for "Programming with ICD2/ICD3". Can the PICKit be used instead or shall I have to buy an ICD?


texts:
Given input X and output Y and a clock - X is a button/switch and Y is equal to 1 only once per clock-cycle and button press.

The button is asynchronous and Y should only switch to 1 at clock rise.

I tried making a a time-diagram, not sure if it helps.

I tried to use D-flip flops but I have not come to any solution.


texts:
I have two SPI slaves connected to one SPI bus on a raspberry. One uses SPI mode 1 the other uses SPI mode 3. In my C++ program I have two SPI_bus objects configured for each mode. If I now try to read each device individually everything works perfectly. But if I try to read both of them in one program I sometimes get communication errors where the communication is not successful (ioctl returns -1)
Could the devices somehow get confused even though they are disabled through chipSelects when writing to the other device in the other SPI mode (clock polarity changes)?


texts:
Purchased a device from an online retailer (fairly well known and reputable), they ship from internationally and often include a local USB wall charger to replace the one in the box of their goods.

Plugged said charger in and it blew immediately. Pulled it apart (because curiosity - it's worth a few bucks so I wasn't bothered to return it). Turns out the control chip (DK112) blew. Had a closer look and noticed something interesting on the underside - does it make sense for that resistor to be there shorting the pins? Worked out that it is between the GND and Collector pins of the chip.

Just curious as to whether the fault is in the circuit design or the chip itself!


texts:
I've been assigned to start working on a smart energy meter project, it's been like 10 years since I put any work in AC. I would be sincerely grateful for any constructive advice. Now the 3-phase meters I'm been assigned to work on are class 1 smart meters and apparently they need to comply with IEC62053-21 power consumption limits for voltage circuits which are as follows

Also the since the metrology part/ front end which consists of,

Current Measurement: Current transformer (isolated from mains, no neutral reference need to be connected).
Voltage measurements (need to be non-isolated and the neutral needs to be connected to the ground of the system) of course any modem or communication device is to isolated.

The Main SOC (MCU+Metrology) is power hog and it apparently draws around 50 mA alone, the rest of the circuit probably another 20 mA maximum. I've been hinted to study the possibility of using dropper capacitor power supplies+ DC-DC regulators which have high input tolerance (60V) instead of transformer based AC-DC ones. I've been gathering all i can to fully understand the circuit to get 12VDC, seems I'm still going no where.

For now my questions are the following:

Which type of power supply type (non-isolated) should I use while designing the power supply (capacitor dropper, etc) 10 VA or 2 W, based on my previous calculations 10VA @ 230V will give about 43 mA which is tiny? I'm confused help?
How do I calculate the power efficiency of the dropper capacitor? I'm aware of the Pout/Pin but since this has capacitor the equation is not applicable?

All my findings and work are available here: https://www103.zippyshare.com/v/U7kgRZK8/file.html


texts:
I have found a similar answer related to taking care of multiple responses in a Dali bus system:

DALI: Handling multiple responses from DALI system

I'm designing the dali control device(master). I have finished the commissioning process and now testing it with 2 control gears. It works well when there is only 1 control gear on the bus. But when there are 2 control gears on the bus, the backward frames have timing problems due to wire-or process. This is already expected, but I'm trying to find out what is the proper way to handle this.

I can use more relaxed thresholds for comparing the timing values but how do we differentiate if it is a wire-ORred response(from multiple gears) or invalid frame(say, timing problem from one gear).

The timing of 1's are almost lower than 250uS and this is way below my threshold for minimum te capture value.


texts: Is the maximum audible noise from power supplies regulated in Europe?

texts:
Power supplies make sometimes a lot noise in the range of kHz. Is there a regulation for the maximum allowed noise emission for consumer electronics on the European market?

Is there a regulation which would protect customers who buy an alarm clock, but can not sleep anymore, because it chirps loud?

Where can I look up, which sound profile a device for the European market may emit?

So far I found only the German "Technische Anleitung zum Schutz gegen Lärm – TA Lärm" and The Outdoor Noise Directive 2000/14/EC (OND).


texts: That's for a homework. I'm asking what is 1/L, where L is inductance? I mean, as the inverse of the resistance is conductance, what is the inverse of the inductance.


texts:
I've been trying to study how the ARM bootloader works, but initialization of SDRAM is still somewhat a mystery to me. For example AT91 Bootstrap uses following function for initialization. I think I understand most of the steps, but why step #7 (8 auto-refresh cycles) is needed?

int sdramc_initialize(struct sdramc_register *sdramc_config,
                unsigned int sdram_address)
{
unsigned int i;

/* Step#1 SDRAM feature must be in the configuration register */
sdramc_writel(SDRAMC_CR, sdramc_config->cr);

/* Step#2 For mobile SDRAM, temperature-compensated self refresh(TCSR),... */

/* Step#3 The SDRAM memory type must be set in the Memory Device Register */
sdramc_writel(SDRAMC_MDR, sdramc_config->mdr);

/* Step#4 The minimum pause of 200 us is provided to precede any single toggle */
for (i = 0; i < 1000; i++) ;

/* Step#5 A NOP command is issued to the SDRAM devices */
sdramc_writel(SDRAMC_MR, AT91C_SDRAMC_MODE_NOP);
writel(0x00000000, sdram_address);

/* Step#6 An All Banks Precharge command is issued to the SDRAM devices */
sdramc_writel(SDRAMC_MR, AT91C_SDRAMC_MODE_PRECHARGE);
writel(0x00000000, sdram_address);

for (i = 0; i < 10000; i++) ;

/* Step#7 Eight auto-refresh cycles are provided */
for (i = 0; i < 8; i++) {
        sdramc_writel(SDRAMC_MR, AT91C_SDRAMC_MODE_AUTO_REFRESH);
        writel(0x00000001 + i, sdram_address + 4 + 4 * i);
}

/* Step#8 A Mode Register set (MRS) cyscle is issued to program the SDRAM parameters(TCSR, PASR, DS) */
sdramc_writel(SDRAMC_MR, AT91C_SDRAMC_MODE_LOAD_MODE);
writel(0xcafedede, sdram_address + 0x24);

/* Step#9 For mobile SDRAM initialization, an Extended Mode Register set cycle is issued to ... */

/* Step#10 The application must go into Normal Mode, setting Mode to 0 in the Mode Register
 and perform a write access at any location in the SDRAM. */
sdramc_writel(SDRAMC_MR, AT91C_SDRAMC_MODE_NORMAL);        // Set Normal mode
writel(0x00000000, sdram_address);        // Perform Normal mode

/* Step#11 Write the refresh rate into the count field in the SDRAMC Refresh Timer Rgister. */
sdramc_writel(SDRAMC_TR, sdramc_config->tr);

return 0;
}


texts: What's the best way to create an IoT services startup?

texts: Let's say I want to create my own apps for specific applications of IoT. What are the best kits for this kind of project that I could sell with my apps? It's okay to use a development kit? Thanks.


texts: I have 4 or 5 of these. Any way to tell what pin is the cathode?


texts: Push-pull power amplifier on complementary darlingtons

texts:
I decided to make a power DC-amplifier. I used complementary darlington pair TIP142 and TIP147. Also TL082 used for negative feedback. The schematic is as below:

I gave 100 kHz sine signal and under oscilloscope I noticed the crossover distortion. It seems opamp is too slow to compensate ±1.4V "dead zone" (distorion on oscilloscope above).

Then I decided to bias darlingtons bases using four 1n4148 diodes as follow:

Unfortunately after 5 seconds TIP147 blew up although transistors were mounted on a heat sink and the fun was over. :D

I was reflecting what actually gone wrong. I suppose that:

I didn't put diodes on the same heat sink as darlingtons.
Consequently BE voltage dropped under the diodes bias.
In Horowitz's "The Art of Electronics" I have read if I we are using
emiter resistors, then four diodes biasing are insufficient.

I would to know are my conclusions correct and also how to effectively get rid of crossover distortion.


texts: Good filter design software for Mac OS X/Unix?

texts:
I need to implement a simple lowpass filter for a data acquisition circuit (using stretch conductive fabric as a resistive sensor). Various sources have recommended that the best way to go about this is to use filter design software.

I haven't found a filter design tool (calculator) that I like yet. The online ones I've found have been buggy/obnoxious. The best solution would be one with a nice GUI that works with Mac OS X. Alternatively a Unix/Linux solution could work. Windows is a no-go for me.

I found this list: http://www.circuitsage.com/filter.html

EDIT: I'm using this web-based one right now, specifically for active filters (which are more applicable for sensors as they are more stable with low frequencies).


texts: SMPS grounding interference ... ground loop maybe?

texts:
I am experiencing a weird phenomenon with my class 1, 15 Volt, 1000 watt SMPS with an isolated input and output grounds.  The AC input (PE) ground connection has continuity to the SMPS chassis.  When I touch the power supply chassis, I get a really loud hash of interference.
Based on the info provided below, can someone offer any tips on how to eliminate this "touch" interference problem?
I have mounted the SMPS in a rather large aluminum cabinet.  The 120 AC ground is connected to the SMPS AC ground (PE) connection and pigtails over to cabinet ground (short run of 3 inches).  On the DC output side, I have a class C linear amplifier.  The circuit board ground, heatsink and coax connections of this amplifier are connected to the cabinet.  In the process of eliminating some high frequency interference to the amplifier I added a differential mode choke (DMC) between the DC output leads and the amplifier, which works extremely well. I also had to isolate the SMPS chassis from the cabinet with a sheet of plastic.  If I let the SMPS chassis touch the cabinet or if I touch it while isolated on the plastic, I get really loud interference.


texts: What exactly is Pole Frequency in a Filter and how does it affect the frequency response?

texts:
I'm having great trouble understanding the concept of a pole in a real world electric circuit. I do understand what a 'pole' is and what a 'zero' is, in the point of view of a 'Transfer Function' but when I'm study bode plots, the definition seems to differ.

WHAT I ALREADY KNOW: (Assuming a Voltage Transfer Function i.e Vout/Vin)

"A pole frequency is that frequency at which the transfer function of a system approaches infinity"

And similarly  "A Zero frequency is that frequency at which the transfer function of a system approaches Zero"

THE QUESTION:

1) Why does the magnitude Bode Plot of the response of a filter NOT approach Infinity at a pole? (and why is the -3dB point at the pole frequency?)

2) In the attached image, why is Wp (Omega subscript:P) called the pole frequency when the denominator clearly does not become zero at that frequency?

3) Dealing in the S domain if a transfer function turns out to be 1/(s+2)(s+3) how can the Negative pole frequencies i.e s=-2,s=-3 be produced physically?What are the poles in this circuit?

I feel I'm missing something very significant here. Please help!


texts:
I found a huge cap-like looking part in an old parts bin of mine. I tried making sense of its marking and I don't really understand what they mean. I googled for the part number and I found eBay listing and such, suggesting it's indeed a cap according to the eBay category, but even there I didn't find further information about the specs of this thing (somewhere it was suggested it's a 40uF 1250V cap but I don't see 40 anywhere written on the part).
Testing it with my component tester delivers very weird results: it's detected as a diode but also with 1.8mF capacitance...?! (usually the tester works nicely and rarely lies to me)
Can you help me identifying this?
Here is the picture:

EDIT: Interestingly, while playing with it again, the tester detected it once as capacitor, with 1759uF and 7.9 ohms ESR. But I can't reproduce it, now it's back to the diode rubbish... Anyway, I don't get how to read these markings correctly.
EDIT2: Multimeter gives me 1755uF.


texts: IR2110 incorrect output waveform from input waveform

texts:
I have a problem that is bothering me for weeks, after frying a couple of MOSFETs and (expensive) IR2110 ICs, I still have no clue. Note that I am still a beginner when it comes to this.

The project I am working on is as follows: I need to drive 40A brushed (cordless drill) motors for my robot at high torque, both directions. Therefore I came up with a dual fullbridge (H-bridge) circuit. One H-bridge for each motor, therefore 8 N-Channel MOSFETs in total, where 4 are on the highside. Whenever I tried to drive the motor it started to whine with the frequency I was switching it, it didn't move at all.

Half of the circuit circuit as follows:

The problem I am getting is that the HO waveform is not as the input HI waveform.

The yellow trace is: signal in high fet(HI)

The teal trace is: signal out hight fet(HO)

The purple trace is: bootstrap voltage (VB)

The blue trace is: source voltage (VS)

ALL IN REFERENCE TO COM(GND)

I hope someone can identify the problem, I've tried several drivers, the IR2110, the IR2113, same problem. Atleast a couple of hints or tips where I should look will be a huge help. Thanks in advance.
Kind regards.


texts:
I have a chinese dc motor controller (YK31C, 350W) which has a connector for the brake. This connector will only interrupt the PWM Signal from the controller and does not short the motor for braking. I have access to the port that can interrupt the PWM Signal and to the Motor port and I try now to figure out a circuit for braking. Actually just a switch that would short both ports is not a good idea, since the dead time should be considered. Anyone an idea how this is normally done?

Edit:

I designed a circuit, but I am not sure if this really can work. On the first image you see the motor controller. It might not work because I cannot interrupt the supply voltage. PWM_OFF will deactive the PWM on the N-Channel MOSFET when grounded.


texts: Should long RF traces be differentially routed?

texts:
I'm designing a phased array controller and as such includes a dozen splitters . The board dimensions are approximately around 10 - 11 cm and the RF traces are about 8-9 cm in length . Would differential pair routing offer significant improvement ? Would using a balun to convert the diff to single ended signal introduce any noise which defeats the purpose of using diff ended routing ?
Operates in C band (4.8 - 5.4 Ghz)


texts: Can a circuit have capacitors in both series and parallel?

texts:
From my understanding, two capacitors (or any electrical elements) are in series if the same current goes through them. Two capacitors are in parallel if they are connected to the same wires on both ends (ie they have the same voltage across them).

If you have  a circuit with just two capacitors, and each plate of the capacitor is connected to the same wire, then aren't they both simultaneously in parallel and in series? This doesn't make sense, because which formula would you use to find equivalent capacitance then?


texts: Simple accessible microcontroller for learning low level digital logic

texts:
Sorry if this isn't the right place for this question- if so, please correct/redirect.

I have a technical background, but as for electrical engineering and programming, I'm really just a hobbyist.

I'd like to identify a microcontroller or IC that I can use for learning digital logic at the lowest level- is this called 'machine language'?

Ideally, it would be a popular device with an active user base/community, and lots of simple projects.

Most importantly, though, is that I want to be able to actually write code at the lowest level, and build abstraction on top of that, all for the purpose of hands-on learning.

recommendations for educational resources like online courses and the like would also be greatly appreciated.

Thanks in advance!


texts: Two port op amp gyrator circuit examples?

texts: I can't seem to find any clear descriptions of how a two port gyrator circuit could be made from op amps. On Wikipedia, for example, it only gives this one port version describing an op amp based gyrator used to simulate an inductance.


texts: Does NRND spell the end for a niche product?

texts:
I'm just wondering about this. Luckily I'm not faced with the problem myself.

If I design a product around a specific MCU and have that produced in a niche market, selling maybe a few hundred every year (maximum), would that MCU going NRND (not recommended for new designs) affect me badly? I can imagine I'd have to start a redesign around another chip... how long would I have to do this? Why does a chip go NRND anyway? Is it due to insufficient demand? What if I were a bigger company and just had an order for 10,000 units - would the manufacturer reconsider their decision?

Does anyone have any experience with this? I'm worrying about this, because I'd like the same design to work for as long as possible.


texts: How to turn on & off 50W LED when already using a driver according to limit switches?

texts:
I have a 50W UV LED that is going to be installed on a UV printer's head. The printer's head raster, as printers usually do. I would like to turn the LED on only when reaching the printing surface and turn it off when when passing it. This is in order to minimize the usage of the LED. This helps to keep it running cooler, for a longer time.

The way I thought to sense the head positioning is using optical "slot" sensors, mounted one on each end of the active printing area.

The LED is driven by a CC power supply which has a potentiometer that controls how much to dim the LED. I would like to set a working point using the potentiometer.

So my question is how to do that exactly in a safe way? I understand that I probably want to toggle between two settings of resistance. LED on represented by a certain setting of the potentiomer and LED off is represented by another setting. A naive approach could use a few relays, however I would rather avoid mechanical switching due to all the noise that it creates and the fear that even after mitigation it might hurt the LED or the power supply.

Suggestions are welcomed!


texts: Which design for a "mic booster" circuit?

texts:
I want to to add about 20x gain to a microphone I have. I tested the following circuit with satisfactory results:

I was going to build a PCB for it, but then I realized I had no NE5532 around in SMD packaging. I found some LME49990, and reading the datasheet I found the following circuit:

So I modified it a little to get a balanced output. I just removed the second part that converts balanced to single ended:

Two questions:
1) Will this work?
2) why is R5 shared between both amps instead of using a resistor to GND like a traditional noninverting amplifier?

My rationale behind the two opamp version is that I have less components in the audio path, so, less chance of adding noise.

Bonus question:  do I need to worry about DC here? Should I add coupling capacitors at the inputs?


texts: Very little amplification when amplifying audio signal with LM318

texts:
I'm trying to build a very simple circuit, that will amplify an audio signal coming from a 3.5mm jack and play it back on a small 32ohm speaker.

I can see that the amplifier is actually amplifying, if I compare the strength of the input voltage versus the output voltage. But the problem is, it's amplification level appears to be only a factor of 6x. Based on the R2 / R1 division, the amplification factor should be around 100x, correct? if I crank up the voltage to 15v, then the amplification factor increases, but not significantly. Why is the amplification factor so low, even through the datasheet states the the amplification factor is calculated based on: R2/R1?

Another problem is that the speakers output is as quiet as an output from headphones. Even if I crank up the power supply of LM318 to 20v - the speakers volume doesn't increase.

As far as I understood, I will get very limited current supply out from the op-amp and won't be able to drive the speaker directly, correct? Do I need to drive the speaker with a transistor to make it louder or what would be the proper method? Thank you for you time.


texts: In my circuit my motor terminals are connected to the output of a VNH5019A motor driver https://www.pololu.com/product/1451. When the circuit is no longer powered I want to allow the user to freely rotate the motor (a dc motor) output shaft (which in my application has a load attached to it that I want the user to be able to move if power has disappeared). Currently if I rotate the motor fast in one direction and then suddenly change direction I can feel a "resistance" to the movement in the new direction. I assume this is because the motor is generating a voltage which opposes the movement in the new direction. Can anyone explain to me what is happening and suggest a modification to my circuit that would prevent this from happening?


texts:
Apart from this edge mounting kit from Adafruit, what are some ways to mount a PCB that does not have mounting holes?

I'm looking for non-permanent mounting solutions that take up little real-estate (visual and physical). So this excludes hot glue, velcro, and zip ties.

The standoffs used for mounting glass and signs for example are a possibility but they do not come in a small form factor or cheaply...

Is there anything you can grab from a local hardware or crafts store that would do the job?


texts: Simple Power Dissipation Questions - Completely Stuck

texts:
I posted a question a few days ago about a simple power dissipation question I was stuck on. I still can't proceed with this group of questions.

In this class I've since moved on to Mesh Analysis and getting the answers correct, but I still cannot solve these problems. From a previous post I saw that combining the 8V supply with the 10A supply would dissipate the required 80w for question 1. But I can't get started on any of the other problems. I written out all possible combinations of resistors in series and parallel, combinations of voltage supplies in series and current supplies but I still can't get anywhere.

Can somebody please explain the process to solving these problems as I missed the tutorial which ran through these problems and aren't getting answers back.

The questions are:

  Jimmy the Circuit Builder has seven circuit elements on his workbench.
  He is trying to build circuits that produce or dissipate specific
  amounts of power from specific elements. The seven elements are shown
  below. They include two voltage sources (4V and 8V), two current
  sources (5A and 10A) and three resistors (3Ω, 6Ω and 9Ω). Each of the
  sources can produce a maximum of 500W. All elements have a maximum
  dissipation rating of 1kW. Jimmy’s workbench has only enough
  connectors to connect three circuit elements together.

  Your task is to design circuits for Jimmy that meet the specifications
  for power from specific elements listed below. Use a maximum of three
  elements from the set above for each circuit. Ensure that no element
  exceeds its power rating.
  Elements can be re-used for different circuits, but not within a given circuit.
  (a) Dissipate 80W from any voltage source. (b) Dissipate 675W from any resistor. (c) Produce 55W
  from the 5A current source. (d) Dissipate 1W from the 9Ω resistor. (e)
  Dissipate 54W from the 6Ω resistor.

In the interests of showing that I'm actually trying - what I've figured out already;
Req in series resistors:
3+6 = 9Ω
3+9 = 12Ω
6+9 = 15Ω
Req in Parallell resistors:
3&6 = 2Ω
6&9 = 3.6Ω
3&9 = 2.25Ω
Resistance in Powersupply & Voltage Supply Combos:
4v & 5a = 0.8Ω - 20w
4v & 10a = 0.4Ω - 40w
8v & 5a = 1.6Ω - 40w
8v & 10a = 0.8Ω - 80w
12v & 5a = 2.4Ω - 60w
12v & 10a = 1.2Ω - 120w

I got the Part A answer from a previous question, so my working for Part B:

  Applicable Formula P=VI, P=I2R, P=V2/R

Must dissipate 675W. My process:
Possible voltage sources are 4v, 8v, 12v. Try to find required resistance to dissipate 675watts
P=V2/R
R=V2/P

42/675 = 0.0237Ω - Not possible
82/675 = 0.0948Ω - Not possible
122/675 = 0.213Ω - Not possible

Possible current sources are 5A, 10A. Try to find required resistance to dissipate 675watts.
P=I2R
R=P/I2

675/52 = 27Ω -  Not possible
675/102 = 6.75Ω -  Not possible

I'm obviously missing something and just can't get it. I must emphasise that I'm not looking for the solutions to the answers but help with how to solve them. Is there a systematic approach like Mesh Analysis on how to solve these problems?
Any help is appreciated.

Update: Tried @Transistors suggestion. Still no luck?


texts: I have seen this question asked before but it was over 8 years ago and I assume things must have changed since then. Basically, I am working on a personal project that I would like to see if I can sell, I made a wearable prototype using an Arduino Nano 33 BLE , all it does is send accelerometer/gyroscope data over bluetooth to an iOS Application I made. I can't use the Arduino in a commercial project and I need something more compact to fit in a wearable enclosure. My question is, is my next step to replace the Arduino with a custom made PCB or are there other options out there now such as pre built boards that can satisfy my BLE, Accel/Gyro , and Small Size requirements? I couldn't find much information besides building a PCB. I would like to keep the overhead as low as possible so if custom PCB is the route then I would be designing the PCB myself (I have never done this before but I can learn) and sending the files to get manufactured. Any insight on the route I should take going forward would be greatly appreciated. Thank You.


texts: Detecting a parasitic voltage/current that differs from line frequency

texts:
I have a question related to electronics:
"Someone told you that there might be a problem with the electrical circuit: In addition to the standard 50Hz alternative voltage, it mights exist another disruptive frequency at 50.5Hz.
For how long, at least, should you measure the voltage in the outlet to know if this disruptive frequency actually exists or if it is a fake information ?"
The answer is 2 seconds, but I can't understand why. Can someone explain? Thanks in advance.


texts: Help identifying this damaged FFC/FPC connector

texts:
I am trying to identify this damaged connector on one of the PCBs of a Konica Minolta Vivid 910 laser 3D scanner. I wish to find a suitable match for replacement.
It connects the main logic board with the LCD via a FFC cable. (The LCD itself has a small board and connector also, although I don't believe the two are the same connector).
The connector has 33pins, and I'm pretty confident it has a pitch of 0.5mm.

The connector width is 20mm from side to side. Although the front facing corners are damaged so it could have been marginally wider.

I am uncertain of the contact orientation however. I seem to see two sets of matching rows, with the lower apparently protruding slightly more. However the FFC cable only has contacts on one side, suggesting the connector would not be dual contact.
From the photos, I'm inclined to think it is a bottom contact connector.

On this photo you can see the FFC end is one sided, and you can also see the dark grey tab/drawer which now does not fit the connector. Pay no attention to the tape botch-job. It was painful to watch, and I'm not sure about the orientation it's presenting the cable in is correct.

For reference here are two photos of the connector on the LCD side.
I believe it is substantially different, especially the big dark grey flap tab.

I do not have immediate access to this board, as it is in my university, but could recheck facts in the near future if needed.
So, to recap: I believe I am looking for a 33pin 0.5mm pitch, probably bottom contact, FFC connector. I am unsure if the clamping mechanism was a flip tap or a drawer tab.
I am also wondering if it matters either way. Since I am replacing the connector can I not basically match pitch and pin numbers and accommodating for cable orientation select any clamping method that seems reasonably adequate?
In any case, matching the original connector would be nice.
I don't think its a complete match but the closest I've got is this Hirose Connector:
FH12-33S-0.5SH(55)
https://www.mouser.es/ProductDetail/Hirose-Connector/FH12-33S-05SH55?qs=Ux3WWAnHpjB322do3zzp5w==
Let me know what you all think. Thank you very much for the help.
P.S.#2
Also, is 33pins an uncommon number of contacts for FPC/FFC? I seem to find less results with 33pins.


texts: How (not) to leave class-D amplifier's input hanging

texts:
I would like to setup an audio solution for Raspberry Pi Zero that consists of a headphone jack and a speaker. The goal is that sounds will be played through an internal speaker, and when a headphone is connected, the speaker shuts off and sound is switched to the headphone instead.

My design consists of two amplifiers.

The first one, a TDA1308 class-AB headphone amplifier, gets raw signal from the Pi via some filters; the output goes to one of those headphone jacks that has "insertion detection contacts".

When nothing is inserted into the jack, the amplified stereo audio signals get combined to a mono signal and is sent to a second, NS4150 class-D amplifier to drive a 4 Ohm, 2W or 8 Ohm, 1W speaker. (the datasheet for NS4150 is in Chinese. I found this English version, but details may differ.)

Here's my schematics draft for my particular project, built up from application circuits suggested by the two datasheets. RAL and RAR are Raw Audio Left and Raw Audio Right, respectively.

Here is a link to that schematics draft.

My problem: when a headphone (or anything that can go into that hole, really) is inserted, pin 3 and 4 of the jack disconnects from 2 and 5, respectively, and my speaker amp's input will be hanging. I do not know if it can handle that. My speaker amp does have a Control pin to shut off itself completely, but I am not positive how to utilize it without messing with the rest of the audio signal. I know that amplifiers are sensitive and testing them on breadboards might not be a good idea (everything here is SMD anyways), so I want to see if I can get a word of wisdom from everyone here.


texts: How to compute electric bill for a server netbook

texts:
I've taken an old netbook and started using it as a tiny game server. I have removed the screen, wifi card and reproductors, but the rest is there (battery, fan, sata HDD). It runs 24/7 and charger is plugged in at all times.

I wonder whether it is possible to compute a fairly accurate estimate of an electricity bill for this machine in both idle and maximum usage scenario.

The computer is Asus EEE 1201HA and adapter has 19V~2.1A output. Also is the energy consumption affected by having battery plugged in?


texts: Measuring Q and Bandwidth of an RLC series circuit using Oscilloscope

texts:
I have a HNC Lab assignment coming up. As part of the prep for the lab work we have been given an RLC series circuit for which we had to calculate some values such as volt drop , Wn, Q and Bs, which I've since done. We then have to use simulation software, in this case Multisim, to simulate the circuit and compare the values measured to the values calculated.

Currently I'm stuck on measuring q factor and bandwidth within Multisim. I'm assuming an oscilloscope should be used but I'm unsure where it should be connected and how to interpret the plot received. I've been searching google for a couple of days but cannot find any information.

The values of the circuit are R 500Ohms, L 56mH, C10nF, Vs 5Vpk @ 10KHz.
I used Wn = 1/ Sqrt(LC) to calculate the resonant frequency, which came to 42.258k. I've confirmed this within multisim.

Any help would be much appreciated.


texts: What are the differences between an AC and DC coil relay?

texts: If a DC coil was just a coil, it would saturate. If an AC coil was just a coil, the magnetic field would drop to zero at 120 Hz and the relay would chatter. Presumably the designs in some way prevent these problems. How? And does it prevent me from putting DC on an AC-rated coil?


texts: Why Altium AC simulation lacks of the math functions available in other analyses?

texts:
In Altium Designer, Mixed Sim simulation, AC analysis, the plots can be modified adding arbitrary combination of waveforms, but for some reason, the Edit Waveform dialog lacks of the mathematical functions available in other types of analysis. Why??
In AC analysis this is the dialog

In the other hand, in transient analysis the dialog has a lot of math functions available in other analyses too.


texts: How to do high switched current from small solar

texts:
I am working on a small, solar-powered application that makes use of RF and a few higher-power sensors. Those will only be on for a fraction of the time, but might consume 1A-2A at 3.3V.

The remainder of the time, a low-power micro-controller will be doing house-keeping, monitoring the charge of a super-capacitor, and enabling the high-power load when enough charge is available (and some other criteria are met).

I have been working with the LTC3108 on this, but this has a current limit of 300 mA, which now proves to be a problem.

Do you have recommendations for other parts, or a combination of parts, that would allow me to tackle this?

My requirements:

controllable 3.3V output 1A-2A (only briefly used)
input from solar cell (e.g. 1.5V, 26 mA peak - but could be changed)
always-on 2.2V or 3.3V output for low-power μC
a super-capacitor that stores the harvested energy (e.g. 2F 5V - but could be changed)


texts:
I have a 12VDC high-head low-flow well pump. It's been running satisfactorily from a couple of 12V solar panels for about 6 months. For most of that time I had it connected to a small timer controller to enforce a 2hr on/30mins off duty cycle in accordance with the manufacturers recommendations. Due to laziness/disorganisation I never got round to weather-proofing the controller and when the rainy season started it get soaked and broke. Since then I've had the panels connected directly to the motor via a float switch.
The other day we noticed that our water tank wasn't filling correctly and it turns out that although the pump is still running when the sun comes out, it's very weak and can no longer lift the water high enough. On measuring the current flowing with a clamp meter, I'm only seeing 0.1-0.2A flowing  despite the fact that the pump is rated at 8.0A max.
Things I've checked/tried:

The pipe isn't blocked - and it behaves the same with the pipe disconnected
Connected directly to a known-good 12V battery, it behaves the same
I disassembled the pump. There were no obvious blockages; the bearings seem fine; there's no visible evidence of the coils burning out; the brushes look fine although there was quite a lot of carbon dust from the brushes (sealed motor unit) which I've now cleaned off
I tried measuring the resistance of the various sections of the motor coils, there didn't seem to be any that were obviously higher/open circuit
No excess resistance in the power cord/ internal connections

Given that it worked for this application before and I've tried it with multiple power sources it seems safe to conclude that something has failed with the motor; and this wouldn't be entirely surprising given that I've been running it beyond the manufacturer's specifications for several months now. But before I give up and buy a new pump (and timer unit!) I was keen to try and pin down exactly what was wrong to avoid wasting money in case there was something else amiss, or, even better, something that I could credibly fix myself.
What else should I check? What other failure modes to these motors have?


texts: Parallel audio is twitching my whole circuit

texts:
I'm still pretty new with electronics and am working on my first multi-voltage circuit.

My circuit is powered by two A23 12V batteries in parallel. From this circuit, I want to power a short section of 12V LED lights (about 4 inches of these cuttable strips).

It will also power, in a parallel branch, an adafruit audio assembly, after a 5V voltage regulator. Here are the adafruit parts I'm using for the audio:

5V voltage regulator
Audio FX Mini Sound Board
Mono 2.5W Class D Audio Amplifier
Mono Enclosed Speaker - 3W 4 Ohm

The below schematic is my circuit essentially...

simulate this circuit – Schematic created using CircuitLab

The 12V LEDs light up and work just fine.
The audio circuit powers up, illuminating the "power on" LED as expected.
However, when I close the trigger circuit on the sound board to actually play the sound, it makes a tiny scratch on the speaker and then the whole circuit just blinks out.

I know that the audio circuit itself is all configured properly. If I disconnect it from the 12V circuit and just connect it to three AA batteries, it plays perfectly.

https://youtu.be/VyevfLwVU6Q - this is a quick video of how the audio sounds (properly) on the simple 4.5V circuit
https://youtu.be/0y5xfyxhmo8 - this is what it is doing when connected (downstream from the voltage regulator) on the 12V circuit
(pardon the vertical video, my phone was horizontal, not sure why it recorded vertically)

The wiring diagrams I found online for hooking up voltage regulators all showed capacitors on each side of the regulator, but they all also said that the capacitors helped to normalize fluctuations in A/C current, which my circuit is D/C.

Any idea what I am doing wrong with the 12V circuit, and why triggering the sound effects blinks the whole circuit out?

If there's any other information needed to help, let me know and I'll do my best to answer.