texts: FET impedance converter (for a non FET electret mic)?

texts:
I have a few electret microphones (KEAG45NPF-W). But these are all without a FET. The datasheet tells me I need to add a 'FET impedance converter.' Now, I'm still learning, and I have a very basic understanding of FET (and JFET.) But the bottom line is, I have not a clue how to interpret this.

Any tips/help how to make this work would be great!

Here is the schematic they provided:


texts: I know that if a second order, type two PLL has only a capacitor as its loop filter, it is unstable because its phase margin would be zero. but why is it ok for a DLL to only have a capacitor as its loop filter and it doesn't need the resistor in series with the capacitor to be stable? (i.e., it doesn't need the zero) and how does this zero in PLLs improve phase noise near the PLL's bandwidth frequency?


texts: Continuous-conversion vs Single-Conversion mode

texts:
I am working with an LSM9DS1 9DOF IMU and was wondering about some of the choices about operating the magnetometer. This is my first time working with an IMU, so I am having some trouble understanding some of the data sheet with it.

One of the registers (in CTRL_REG3_M) says the system operating mode can be continuous conversion, single conversion, or power down mode. I don't know what the difference between continuous and single conversion mode. I believe this has to do with how the ADC operates, but some insight into the significance of this would be great.

Another register (CTRL_REG5_M) has something that seems similar called block data update. Does this mean that in one case, when I read the output it will update the output register, but in the other the output updates continuously, whether being read or not?

My goal is to sample the magnetometer the magnetometer either at its maximum output ODR of 80Hz, or perhaps faster so that my data rate for the magnetic field corresponds to the data acquired from the accelerometer, which I have set 119 Hz. But I was wondering if these two settings above would have any implications for handing this procedure.

Thanks for the help!


texts:
I am concerned about an ultracapacitor (2.7v, 3000F) that I received today. I set my power supply to 2.5v with a current limit of 1A, then connected a diode to the positive lead such that current would only flow to charge the capacitor. I then connected the end of the diode to the positive terminal of the capacitor and ground from my PSU to the negative terminal of the capacitor.

However, only about 2mA was drawn. The diode I am using has a low diode drop (~0.3v), so I figured it should still charge the capacitor to around 2.2v. I then adjusted the voltage such that there would be 2.7v across the capacitor (~3.0v from the PSU), and it slightly increased the current drawn, but the change is negligible.

I can't see anything wrong with this charging setup, so is it likely that the capacitor is bad? Perhaps the polarity indicated on the capacitor is incorrect? Is reverse voltage harmful to ultracapacitors, meaning that I shouldn't check? Thanks.


texts:
I'm designing a 4th order chebyshev filter. I decided to implement it with two tow thomas filter. I've calculate the poles, but I don't know how to calculate Q and w0 for each tow thomas.

How do I calculate Q and w0 for a 4th order chebyshev filter?

Problem solved. Thanks to everybody


texts: Transformer with a single turn plate as secondary

texts:
What kind of applications are transformers with a single turn secondary used for?
I believe a high current is generated, but couldn't really figure out a good practical example where this might be used.


texts: Occasionally the first byte of data from an SD card SPI read is bad

texts:
The device I am developing is an SD card storage add-on to a retro computer, SanDisk Ultra II 1.0 GB SD card in an SD card socket (I have no idea if the brand is significant, it just happens to be what I have).

The SD card is the only device on the SPI bus; a level shifter ensures the card is fed signals at 3.3 V; MISO feeds via bus-switch to a 3.3 V FPGA.
The FPGA implements a clocked shift register mechanism, which clocks eight times, shifting out output data to MOSI and capturing input data from MISO.

Many devices attached to many computers work fine.

I use SPI mode. I initalise the card, speed it up to 4 MHz, and send the read single block command.

I observe that first data byte returned occasionally has a one-bit corruption. Typically bit 0 is set when shouldn't be, but I have also seen bit 1 set when it shouldn't be. All other bytes are perfectly correct, always.

Multiple devices were tested attaching to multiple host computers. The problem was only seen with one device attaching to one computer. The device or computer works fine with other computers or devices.

I suspected timing errors in my driver code, but I am sure I have done the eight clock cycles (sending 0xFF, reading first data byte) before I read it.

I'm wondering, could this be related to voltage or current levels, which might be subtly different depending on device or computer?

I'm wondering, does an SD card suddenly need to draw extra current, just as it starts to output data?


texts:
I am trying to build a LFO circuit that produces a wobble bass effect.

My overall plan is using an Op Amp to create the LFO and another Op Amp to create the low pass filter. How should I connect these two stages? I know that the LFO part will output a square wave, but how do I use that wave form to change the cutoff frequency of the low pass filter?

I know that the easiest way to change the cutoff frequency is to change the resistance, but how do I achieve that with the out put from an Op Amp LFO?


texts: DC permanent magnetic motor control issues

texts:
We have a 180 V dc permanent magnet motor.

When engaging the control board while the motor is hooked up. The output to motor drops out and reads no voltage. If I take the motor leads off the board and fire the controller the outputs will read 180 V just like it's supposed too. So when the motor is hooked up to the board we get 0 V, when it's not we get the 180 V that is intended. We have tried switching out the board and also the motor and still get the same outcome.This current setup has ran perfectly fine for the last 20 years. Three days ago this problem occurred. The wires from the board going to the motor are fine. Nothing has changed as this is not a new setup.


texts: How do you create an isolated, positive voltage?

texts:
I know this seems like a simplistic question, but I am a beginner here....

Multiple web sites pop up on Google talking about how to create a negative voltage, but what about positive?

The Wikipedia page, for instance on 'field-ion microscope' talks about the necessity of creating (and maintaining) a positive voltage in the tip....


texts: Maximum current is drawn from a cell when it is shorted. But, why?

texts:
First, I must apologize for the trivial-sounding question. We've only recently started with Current Electricity in class, and our teacher posed this question (well, something similar) to us.

  For what load (resistance) will the current drawn from this (simple) circuit be maximum?

Where E is the cell's EMF, r is the internal resistance of the cell, V is the terminal voltage of the cell and R is the resistance of the load.

It was pretty obvious that we'd be able to draw maximum current from the cell if we shorted it...however, we were asked to prove it.

Now, I already knew,

$$V_{cell} = IR$$

Where.

$$V_{cell} = E -Ir$$

So, for a given cell, I assumed V to be constant. In that case, current I is inversely proportional to load resistance R. And since the lowest, real value of R is zero, maximum current would be drawn when the cell is shorted across its terminals.

$$I = \frac{V_{cell}}{R}$$

According to this equation, for R = 0, I'd get infinite current.

My teacher has provided a different proof instead.

  We have the equations,

  $$V_{cell} = IR$$

  $$V_{cell} = E -Ir$$

  So, combining them, we get

  $$IR = E - Ir$$

  Which when rearranged gives,

  $$I = \frac{E}{R+r}$$

  Clearly, for a given cell, the maximum current is drawn for the lowest value of load resistance, which is R = 0. And the maximum current will be

  $$I = \frac{E}{r}$$

[A finite current! :O ]

This is confusing.

Both my "proof" and the one my teacher supplied seem logical. Both our conclusions, qualitatively, make sense (Maximum current when R = 0).

But my "proof" suggests an infinite current will be drawn from the cell, whereas my teacher's proof shows that a finite current ( equal to E/r ) is drawn.

Questions:

1) Where have I gone wrong with my "proof"? It doesn't seem like I've messed up the math... but when compared to my teacher's proof, the infinite current thing doesn't sound right (Hence my assumption that I'm the one who's in the wrong here). Perhaps, I interpreted my own "proof" incorrectly?

2) What would be a better proof (if you know of one) of the fact that current drawn from a cell (with finite internal resistance) is maximum (and finite?) when R = 0?

Additional question (Since this from the same vein as the previous two, I feel it's best posted here instead of in a separate post)

3) I've been told that maximum power is drawn by the load in such a circuit (the one my teacher provided) when R = r. This sounds a little off. Isn't power proportional to current (Since P = VI, and for a given cell, V is constant)? Since we already know that current is maximum when R = 0, shouldn't it make sense for the power to be maximum when current is maximum (i.e- at R = 0)?


texts: I want to make a code for the power vs wavelength for the split loop cavity resonator. Can someone help me with the python code for the same?


texts:
I like to use enameled copper wire where rubbery insulation would be a pain.
Recently I embarked on an electronics project with some lights that would look a lot better if the wires were silver color instead of copper or red enamel.
I’ve seen ‘fairy lights’ all over amazon which feature several small LEDs in parallel across what appears to be enameled silver-looking wire. I could not find reels of this wire anywhere online, however.
Do these ‘fairy lights’ use plated copper wire that then gets enameled? Also, where can I get ahold of some?
I imagine it must be plated, as much of the insulated wire I have in the shop looks silvery when stripped, but the cross-section is distinctly copper.
Update:
Here is a close-up of the "fairy lights" from Amazon:

Even more zoomed-in, the insulation is barely visible:

Update 2:
The wire is not magnetic in the slightest. I took a long piece of it and slowly moved a powerful magnet near the end. No movement at all.
Update 3:
Here is a close-up of the cut cross-section. It is most definitely a copper variant core. I could do a resistivity test and break out my calipers to further test my hypothesis, but this seems unnecessary.


texts: Transfer function of cyclic block diagram

texts:
I have this block diagram, and I just can't arrive at the transfer function \$H(s) = \frac{y(s)}{u(s)} \$

Starting from the end, we see that
$$y(s) = xC $$
Let's find out what x is.
$$x=\Bigg[\bigg(u(s)-x\bigg)A-y(s) \Bigg]B $$
But as you can see from the equation, it is recursive. I also can't see how the block diagram can be simplified, since nothing is in series or parallel. I hope someone can help me out.


texts: Arduino USB not detected in Device Manager

texts:
I have an Arduino Uno version 2 which was working but now is not detected in Device Manager.

The same cable works my AVRISP mk 11 fine and this device is detected.

I can program the ATmega328 via the ISP connection but I need the USB link for debugging.


texts: Fermi level upto which Boltzmann approximation can be made

texts:
Thou this is a solved excercise problem but I have a doubt.
Since
$$ N_0=n_i* \exp{\left(\frac{E_{F_i}-E_F}{kT}\right)}\text,$$
 so for Boltzmann approximation to be valid we should take limiting condition as \$E_{F_i}-E_F=3kT\$ then why instead of this in this example \$E_F-E_a\$ have been assumed to be \$3kT\$.


texts: I wish to use a two gate latch to control a 555 timer.The goal is to turn off the output by shutting down the IC.Will this happen if I disconnect the positive supply or the ground so there will be no current flowing trough the timer?Or,if this won't work,which way should I do it?The 555 is set in the astable configuration.


texts:
How to calulate output voltage level (U2) for a frequency ten times greater than cutoff frequency? ]
for example :
U1(input voltage) = -14 dB?

Or in second case. What is the output voltage level (U2) for a frequency that is 10% of the cutoff frequency? U1 = -14 dB


texts:
What is the difference between Atmel ICE, Atmel SAM-ICE and Atmel JTAGICE mkII?

From what I understand, Atmel ICE is cheaper and better in every way, support more families, thus why would one buy the other one?


texts:
This question refers to the link below:
http://www.brighthubengineering.com/consumer-appliances-electronics/102752-the-longley-rice-propagation-model-and-tv-white-space-for-ultra-wifi/

What does this line means:
In other words, this radio propagation model forecasts long-lasting median transmission loss across asymmetrical terrain relative to white-space transmission loss.

Can anyone please explain?


texts: Powering opamp from unregulated DC-DC Converter?

texts: When using one of those unregulated, isolated DC-DC bricks (its output voltage can be as much as a few volts higher than its rating and varies with load) to power an opamp is a voltage regulator a good idea even if the opamp can handle the higher voltage? What would be some of the benefits of doing this?


texts: Multiple devices on a singe SPI on LPC1768

texts:
I am in the middle of a custom PCB design using LPC1768.
In fact that, this is an upgrade project from Atmega2560.

I am using two LCD's from a shared SPI0 on LPC1768.
When I was using Atmega2560, I had to use two series resistor (4.7K) in CLK and SDA lines.

I have wired two LCD's without adding resistors on LPC1768 and It seems to be working OK.

In the datasheet of LPC1768, If I am not missed, I couldn't see anything mentioned regarding multiple slave devices on the SPI bus.

Is there a rule of thumb on that or LPC1768 has some counter measures internally or I am too picky?

Thanks a lot for your inputs from now.

EDIT:

Sorry for the confusion. My Net-Names are not proper appearantly.
I use a pin's other functions. In this case it is SPI.

SCK means SCLK

SDA means MOSI


texts: Function generator to test filter capacitors

texts:
I'd like to be able to see the effect that a filtering capacitor has on a voltage source with waves at different frequencies, for learning purposes.  I'd like to try to calculate the correct capacitor for a specific wave / frequency, and be able to test it was well.

I was wondering if a function generator connected to a circuit with the capacitor would work for this purpose.  I already have an oscilloscope for visualizing the voltage graph.

Also, is there anything I should take into consideration when picking a function generator to buy?


texts: Vertical distance from PCB antenna layer to ground plane?

texts:
I know the basic design requirements for pcb trace antenna, no ground place below or above the traces, impedance matching etc. But the design layout recommendations for pcb antenna doesn't seems to answer my question.

My circuit is very small and I also have multiple PCB stacked one above the other (similar to the iphone X motherboard).

My question is what is the safe distance from the trace pcb antenna to other vertical grounds? i.e. imagine i have 3 pcb 1.6mm stacked one above the other with the top being the antenna. Can I have a GND place on the bottom pcb, between 3.2 and 4.8mm below the trace antenna?

Edit: Found this SMD antenna that they say that doesn't require GND clearance: 2.4 GHz SMD On-Ground Antenna


texts: Create a new wireless protocol for industrial

texts:
I'm working on project that lets industrial machines communicate to each other wirelessly. It seems that Zigbee at 868MHz is the best choice (if you have any other suggestion it would be great), considering range ad penetration capabilities.

Recently I've been asked if it could be easier to communicate over radio waves and create on top of it an ad hoc protocol, instead of buying Xbees modules which are expensive.
That would allow me to buy cheaper radio modules.

I don't have much experience in radio communication and protocols, but it sounds complicated to me.

What do you think? Does it make any sense? Thanks!


texts:
Could you help me identify a smd transistor that has the following code: N3L1 (Sot23)
thanks for your help


texts: What is the use of the diode in this circuit

texts: In this circuit, a diode is connected from emitter to ground. What is the fucntion of the diode in this circuit? What I thought of it is, the diode appears to be in forward bias and so is the base emitter junction. Hence, there is no need for the diode but, when I checked the solutions, it says the diode is to protect the base emitter junction from reverse breakdown. Can somebody please explain me?


texts:
I'm using Multimedia logic for this particular assignment, I am to implement an ALU that performs Bitwise Rotation on the input from "A" by the amount defined by "B". Not quite sure how to approach this.

New to the topic in general, so not quite sure what other information to provide, please let me know if I am missing something


texts: Air core solenoid Melting when given 3amps with neodymium magnets as core

texts:
I'm currently using magnets and ferrofluid in an art project. I'm not experienced with electrical engineering but maybe that will be obvious after reading this question.

I'm currently using this air core solenoid

https://www.schoolspecialty.com/science-first-air-core-solenoid-532015?gclid=CjwKCAjwyMfZBRAXEiwA-R3gM5FUxM-X6lp6yX7O-YWdqZLMyAb1wgY1hNIZ70pZ9scEdL1RDXTGBRoCHm0QAvD_BwE

hooked up to this power adapter https://www.amazon.com/gp/product/B078RY7BPL/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

The power adapter outputs 3 Amps and the air core solenoid supposedly can take 5 amps. The positive terminal was hooked directly to the power adapter and the negative terminal was hooked up to a relay which in turn was connected to the power adapter.

Inside the core I have a stack of 20 neodymium magnets found here

https://www.amazon.com/gp/product/B071ZKQ2X5/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

I have a sensor hooked up to an arduino that turns the relay on and off based on input. This makes the strength of the magnets inside the core increase and decrease in power based on whether the power supply is turned on.

In this sense it actually works great. Unfortunately it ended up heating up so much the plastic inside the solenoid melted.

Is there something wrong? Do I need to supply it with a weaker power supply? Does it have to do with the power of my magnets?


texts: Doubts about IIR filters definition and transfer function

texts:
I have some basic doubts about IIR digital filters.

My first question is about its definition. IIR means Infinite impulse response, so my question is: is it physically possible to realize such filters? Does infinite impulse response means that it is different from 0 for all negative and positive times (from - infinite to + infinite)?
My second question is about the input - output relation in time domain, which is the following one:

Which is its meaning? "A linear combination of the output samples is equal to a certain linear combination of the input samples"?
If we apply Z - Transform to the previous expression in time domain, we get:

This is due to the time - shift properties of the Z - transforms. What I do not understand is how we have many output terms (for different k) in time domain, while we have only 1 output term (Y(z)) in Z - domain, and the same for the input.


texts: Why does channel length modulation occurring in mosfets decrease the gain of amplifiers?


texts: What is the difference between Instantaneous current (i) and current (I) in a purely inductive circuit?

texts:
I was reading about AC inductor circuits on All About Circuits:

Link: https://www.allaboutcircuits.com/textbook/alternating-current/chpt-3/ac-inductor-circuits/

Consider this circuit of a purely inductive load:

I understand that to calculate the instantaneous voltage (e) dropped across the inductor (L) for an instantaneous current (i), I use the formula

e  = L (di/dt)

I then read this:

  "An inductor’s opposition to change in current translates to an opposition to alternating current in general, which is by definition always changing in instantaneous magnitude and direction"

And thus to express this opposition to alternating current, we have inductive reactance (XL).

They then show that to calculate the current (I) flowing through the circuit (and inductor), we use this formula:

V = (XL)(I)

My confusion is: is there a difference between the instantaneous current i and the circuit current I? Is the current I the rms of the instantaneous current?


texts: Multi-cell LiPo charging from 5V USB, without boost circuit

texts:
For various reasons I'm happy to describe in the comments section, I would like to charge large (>30S @ 1-30Ahr) packs directly from USB. Speed is not critical and multi-day (or week) charging is not an issue. However, what is an issue is size, safety, and complexity, which are hard to come by at these cell counts (unless you have an extensive engineering department to test, test, test).

I reason that since a USB supply is 5V (@ 500mA-5A, depending on PD or not), it's conceptually easy to inject power into a 4.2V cell. If we could split the pack up into individual cells we could connect each cell to the 5V supply and let it soak up some charge.  No need to develop any kind of switching mode power supply or balancer.

However, in a real-world case, these cells are inseparable and so the charger has to deal with the fact that there might be 100V or greater across the pack. Furthermore, the devil is in the details, since pragmatically it would be very dangerous (i.e. prone to user failure) to completely charge one cell before moving on to another.

I feel like the below approach should work for an arbitrary number of cells. The idea is that a microcontroller switches on both ground and positive terminals for a single cell, while switching off all other cells. A zener diode protects against the microcontroller running amok and trying to overcharge the cells.

The system switches at a high rate ("high" as determined by the LC filter)
An LC smooths the current so that the battery isn't seeing a sharp PWM signal
A zener diode provides passive protection against the microcontroller running amok and trying to overcharge the cells
Requires a USB power supply with good current regulation (to keep itself from blowing up)
Not drawn are all the things required to make this work in a real-world setting, e.g. appropriate FETs vs transistors, the sensing circuit to measure input current, voltage, temperature; PWM control of the input voltage; current limiting through the zener diode, etc...

Seems simple, does it work as easily as this? Are there some obvious pitfalls in this design?

My working assumption is that this doesn't exist in the market because most people don't want to charge a >1kWhr, 100V battery off of USB. If I'm wrong, please use the comment section to disabuse me of this notion.


texts:
I'm trying to replace a bad diode in my Chevrolet Captiva C100 rear wiper motor circuit board.
The marking on the SMD diode says SM 03 and I could not cross reference the marking with the correct type of replacement diode.
The good diode has forward voltage around 0.632V and its physical dimensions are 4.0mm x 2.5mm x 2.0mm.
Any help to identify the diode is much appreciated.


texts:
Issue
I am trying to power something that requires 16A of current using 3 different power supplies.
Background

I am not sure how much current my power socket can output or how I might go about checking this.

I am assuming for now that it is only 10A just to be safe.

I am wondering if there is any way that I can power this thing that requires 16A of current.

Possible solution
In the instructions it says:

if operating at home, please power it via two sockets located on separate power rails

I am not exactly sure what this means or if I even have two separate power rails. Could someone please explain to me how I might go about using two separate power rails?
Thank you!


texts: 12 Vdc Intel fan tachometer output to 24 Vdc PLC input

texts:
I'm working on a cooling fan rotation supervision system, and I'm planning to use my old 4-wire Intel E18764 12 Vdc cooling fan to test it (as I don't have access to the 24 Vdc actual fan I'm going to eventually use) but I'm not much of an electronics guy so I was worrying if I'm doing it right. I need ~24 Vdc signal from the open collector tachometer pin for my PLC digital input. The 12 Vdc source for the fan is at the moment actually a 9 Vdc battery. Can I do it like this with a pull-up resistor?

In my fancy-pancy LTspice model it seems to work, but I don't know the actual characteristics of the internal transistor of the fan so I don't trust it (nor my skills in using the program).


texts: How to eliminate oscilloscope channel DC bias

texts: When I set channel 1 as DC coupling, there is always -5.6v bias, even no cable is connected. Can someone tell me how can I eliminate this bias? Thank you


texts: When using conventional means to control a heating element, how does it affect the peak required VA?

texts:
This question is similar to two others, here and here, but with a small difference.

To allow a bit of context: Suppose I have a winters day with lots of sunshine. I have an off-grid PV system, and the PV modules are making more power than can be used at the moment. My inverter is however limited to 1600VA, which limits what appliances I can use to dump this excess.

I also have a 3kw hot water cylinder, which presently runs from grid power. It has a standing loss of at least 2kwh a day, and there is a good 5kwh space between 55 and 85 centigrade (assuming 150 liters of water). It would make a good candidate for dumping excess, especially in winter when more hot water is used.

I can obviously not do this at full power due to the small inverter. In theory, however, the heating element has a power factor of 1 (or very very close), and if I drive it at half the voltage/current it would just take 4 times longer to get the same heat in there, but it should still work.

Traditionally you would do this with something that resembles a dimmer switch, some kind of PWM control, or you'd just rely on the thermal mass of the water and turn it full-on/full-off, but that can't be done here due to small inverter.

My question here: How does it affect overall required VA (because inverters are rated in VA, not watts) if you use something akin to a dimmer switch or PWM control? The overall average consumption may be below the inverter rating, but if it does so by creating extremely high current spikes at low duty cycles, I cannot imagine the inverter would like that very much.

I suppose you can shorten this question to: Can you use a dimmer switch (of sufficient capacity) to drive a large heating element from a small inverter. I have a feeling the answer is no. What are the alternatives?


texts: (Electret Microphone) Why is input taken from the capacitor?

texts:
Why is the input signal taken from the -ve side of the capacitor? I do understand that the resistor has been added for voltage divider.

Is this actually for filtering purposes? Or is the capacitor there just to block the DC?


texts:
I am trying to get the PWM subsystem on a PIC16F887 working. I've gone over this several times and just cant seem to find my problem.
This is part of a larger program, but for simplicity I re-wrote just the PWM portion. I am using the datasheet as my guide for configuring the PWM subsystem, specifically page 131. I am not really worried about getting a specific frequency or duty cycle out. I am just trying to see some kind of waveform out of the PWM pins.
Code compiles fine, but I get no output from RC2.

Thanks for any help
Not sure why the tabbing of the code got a little mangled when pasted into this question.

Board: PIC16F887 c/w 44-pin demo board (Microchip).
Programmer: PICkit3
Compiler: gpasm

;*******************************************************
;Notes
;PWM is used on CCP1 which is P1A which is RC2
;********************************************************
    INCLUDE registers.asm
    __CONFIG 0X2EFF20E5

    ORG 0x00
    GOTO    MAIN

;******************************************************
;Main Program Loop
;******************************************************
    ORG 0X05
MAIN
    CALL    SETUP
    CALL    SETUP_PWM
wait
    BTFSS   PIR1,1  ;TEST TR2IF
    GOTO    wait
    BSF STATUS,5    ;Select Bank1
    CLRF    TRISC   ;START PWM
    BCF STATUS,5    ;Select Bank0
    BSF PORTD,0     ;ENTERING MAIN LOOP
main_loop
    GOTO    main_loop

;****************************************************************
;Setup Subroutine
;general setup
;****************************************************************
SETUP
    BSF STATUS,6    ;SELECT BANK 3
    BSF STATUS,5
    MOVLW   0X00
    MOVWF   ANSELH  ;CONFIGURE ALL PINS FOR DIGITAL IO
    MOVWF   ANSEL
    BCF STATUS,6    ;SELECT BANK1
    BSF OSCCON,4    ;OSCILLATOR TO LOW SPEED
    BSF OSCCON,5
    BSF OSCCON,6
    MOVLW   0XFF
    CLRF    INTCON  ;DISABLE INTERRUPTS
    CLRF    TRISD   ;PORTD AS OUTPUT
    BCF STATUS,5    ;SELECT BANK0
    RETURN
;********************************************************
;SETUP PWM MODULE
;********************************************************
SETUP_PWM
    BCF STATUS,6    ;SELECT BANK1
    BSF STATUS,5
    MOVLW   0XFF    ;DEFINE PORT B AS INPUT
    MOVWF   TRISC   ;PORT C INPUT
    MOVWF   PR2     ;SET PWM PERIOD TO 33ms

    BCF STATUS,5    ;SELECT BANK0
    MOVLW   0X0C    ;SET FOR SINGLE OUTPUT ON P1A AND
    MOVWF   CCP1CON ;ACTIVE HIGH. LSBS OF DUTY =0
    MOVLW   0X25
    MOVWF   CCPR1L  ;SET HIGH BITS FOR DC=50% (Roughly)
    BCF PIR1,1      ;CLEAR TMR2IF
    BCF T2CON,0     ;SET TIMER2 PRESCALER TO 1
    BCF T2CON,1
    BSF T2CON,2     ;START TMR2
    RETURN
    END

As Requested, registers.asm

;*******************************************
;ANY BANK
;*******************************************
STATUS  equ 0x03
INTCON  equ 0x0B

;*******************************************
;Bank 0 Registers
;*******************************************
PORTB   equ 0x06
PORTC   equ 0x07
PORTD   equ 0x08
PIR1    equ 0x0c
T2CON   equ 0x12
CCPR1L  equ 0x15
CCPR1H  equ 0x16
CCP1CON equ 0x17
CCPR2L  equ 0x1b
CCPR2H  equ 0x1c
CCP2CON equ 0x1d

;*******************************************
;Bank 1 Registers
;*******************************************
OPTION_REG  equ 0x81
TRISB   equ 0x86
TRISC   equ 0x87
TRISD   equ 0x88
PIE1    equ 0x8c
OSCCON  equ 0x8f
PR2 equ 0x92
WPUB    equ 0x95

;*******************************************
;Bank 3 Registers
;*******************************************
ANSEL   equ 0x0188
ANSELH  equ 0x0189


texts: Explanation of the current-voltage relationship of a capacitor

texts:
I came across the following statement in a textbook:

  The voltage on a capacitor cannot change abruptly. According to

  $$i(t)=C\frac{dV}{dt}$$

  a discontinuous change in voltage requires an infinite current, which is physically impossible.

How does this relationship prove that a discontinuous change in voltage requires an infinite current?


texts: Thermocouple noise causing spurious reading with SSR

texts:
I have a thermocouple PID SSR heater as shown, based on the MAX31855 ( datasheet ). I get spurious readings when the arduino is plugged into my laptop, my laptop is plugged in to its charger, and the SSR is active.

I'm getting a lot of spurious readings coming from the chip, which frequently returns error codes indicating a short to ground (SCG Fault), short to V+ (SCV Fault), or both simultaneously (not sure). These errors are quite frequent (up to several readings in a row), depending on read rate (1-10 Hz) and whether the SSR is currently on. SSR on = way more likely to error, see graph below. When temp input is above setpoint, there are very few spikes.  I can ignore these errors and get a quasi-accurate reading, but the result is a several degree excursion.

(Temp read °C is in orange , PID (raw) output (+200) is in green, X axis is in seconds. Output of PID algo is clipped to [0,1] so any negative number is pinned to 0. )

Slowing the chip read rate seems to improve the readings, but only slightly, and at the expense of PID responsiveness. This system is very touchy, and a PID misfire of only a second can cause a multi-degree excursion.

I tried modifying the firmware to turn off the SSR (and wait 17 ms to ensure zero-crossing) during the temperature reading, but it does not really seem to help.

UPDATE:

I must note that the above setup is taken on my workstation - arduino microUSB plugged into laptop, which is plugged in to laptop power supply,  ethernet, HDMI to second monitor, and keyboard. When I unplug the power brick, no improvement, but when I unplug EVERYTHING from the laptop save for the arduino, the spiking goes away. Ground loop?

Laptop peripherals unplugged @ 550s.

UPDATE 2:

I just A/B/A/B tested plugging in the power brick. The spiking readings definitely correlate with the power brick being plugged in. Question is, why? I've updated the image to show the earth connections more explicitly.

UPDATE 3: I measured a 1kΩ resistance between the laptop power brick's negative (Vdd) and earth ground. This is probably the punchline. I suspect line noise is propagating from the SMPS through earth ground or maybe live/neutral, coupling to the TC, and screwing with the MAX chip's readings.


texts: MOSFETs blowing up on BLDC motor controller upon battery connection

texts:
I'm trying to build a sensors motor controller for a 500 watt bicycle hub motor. The problem I am having with it is when I connect power (4500 mAh 12s lipo) I usually destroy a transistor or two immediately.

At first, I figured the problem was too much current in the MOSFETs so I got bigger ones capable of 120 amps, 480 amps pulse (much more than the battery can even do) and it still broke the transistors, although not quite as loudly.

Next I figured that timing could be the problem, so I left the MCU disconnected when I applied Vcc - issue still occurred.

I then added pull-up/pull-down resistors on the bridge to make sure they weren't in some kind of floating phase - issue remained.

I also tried hooking up things in a variety of orders such as with/without the motor, with/without the MCU, but I still get the same problem.

Let me clarify a few things about the schematic:

High side are P-channel, low side are N-channel, 100k resistors on the pull-up/pull-down, schmidt trigger mainly to invert signal to P-channel so they are active high from MCU (ATmega328). No gate resistors (from what I read this only slows down switching which could make matters worse).

I really am lost as to what the problem could be here. I still haven't tried putting pull-up/pull-down resistors on the drivers or messing with the code too much, because I figure the code doesn't have much to do with it at this point since the issue occurs without hooking up motor or MCU. I wanted to stop for a minute and see if I'm missing something obvious before I go on, because I feel like I'm just rapid firing trivial changes at this point.


texts:
I have a water pump rated 650 W and the attached relay board.

Is it ok to modify a power socket to use one relay to control the phase and one to control the neutral wire?

Thank you!


texts: I am looking at a TI level translator and need a certain current drive strength.  However, in general, what datasheet parameter corresponds to this so I can make sure I provide enough drive?


texts:
I have a piece of electronics that acts as a event sensor and its trigger voltage starts around 3.3V. Lets say that I want to little bit hack this device and hook it up to a button that is on other device. I found out that when I press this button, LED will turn on and there is about 2.3V that can be measured one resistor. If button is pressed again, LED will turn of and there will be 0V.
I want to make this button as an input to the event sensor, but 2.3V is too low voltage to trigger it. I could use Arduino that would read input voltage and I can define trigger threshold there. But I want it to be simple electronics, passive and efficient. Maybe MOSFET or BJT? Can someone give me advice how to do it?
Thank you


texts:
I'm trying to monitor the temperatures at various location inside and arround my house. So far, I used battery powered (18650 Li-Ion) ESP8266 chips with a DHT22 sensor. The ESP wakes up every 5 minutes, measures the temperature, and goes back into deep-sleep mode. This way, I can run them for approx. 1 month until the battery is low.
Since I don't want to change batteries every month, I read some articles about alternative ways to do that, and learned that Bluetooth Low Energy or Zigbee boards are far more energy efficient and could even enable button-cell battery powering instead of the big Li-Ion Battery.
I decided that I want to try this out with the Zigbee protocol (feel free to change my mind), because it can cover greater distances and i can set up a mesh network. However, I'm really struggling to find resources. I'm not very experienced in this field and I could really need your help on the following topics:
Which Board to choose
It seems like the Xbee boards from digi are the way to go. However, I can't find any real datasheets/specifications about the pins or how to program them. Also I don't find any real alternatives to compare them. (I would prefer a chip-solution, such that i can do all the wiring/soldering myself as with the ESP8266). Do you know any alternatives or any other Low-Power Zigbee Boards? I need:

4 digital IOs (2 for data, 2 to supply the sensors with power once the board is awake)
Low Power Application (Deep Sleep mode)
As compact as possible (no ext. antenna)

Any similar work?
Do you know a similar project I could maybe get some hints? It seems like most people just use the ESP8266 for such applications, and I can't find any similar Zigbee projects.
Tips
Do you have any tips on how i should start this project?
Thanks in advance!


texts: Can I connect the negative terminals together on two LED drivers?

texts:
I have a white, adjustable-color-temperature LED strip that I'm trying to power. The LED is basically composed of two separate LED circuits -- one at 6500K and another at 2700K. The strip has one positive lead for each circuit and a shared negative lead.

Can I connect matched, constant voltage, dimmable LED drivers like this? Is that crazy?

simulate this circuit – Schematic created using CircuitLab


texts:
Please see these two part of this board :

In your opinion, What's the usage of the R32 resistor? also in the AN2867 aplication note has been mentioned:

Then we have to put a resistor to limit the inverter output current (I mean Rext). then What's really the usage of the R32 resistor?

An unrelated question, Should I always connect the RTC crystal(32.768Hz) to the ground?(I mean the shield of it)


texts: I'm doing a project on humidity monitoring using HR202 Humidity sensor and PIC16F877A.I could not find resolution & accuracy of HR202 in online.So please help me to calibrate and use HR202 humidity sensor(not module).


texts: The Transistor Menace - Questions regarding an Arduino rgb LED project

texts:
I've been browsing this forum and the internet now for a couple of days and what I thought would be an easy side project turned into a (for me) quite complicated matter.

I'm planning to build a mood light that consists of 12 common cathode rgb LEDs with each colour being controlled by an Arduino's PWM pins.

In this diagram that has been posted here a while ago I found pretty much the outline for all that I want to do:

My research took me so far to understand the basic matters of a needed external 12 V Power source and the fact that I'd have to wire the LEDs parallel with respective resistors on each.
What I would need help with is what transistors to choose and what resistors for them:

Should I use normal PNP transistors or a MOSFET? Are there specifically recommendable versions of each? And which resistors would I need in front of the transistor?

Important to me is, that one can control the individual colours smoothly and that there is not so much heat generation that I'd need a sink.

I'd appreciate any help,

Cheers
Tim


texts: Does a chip retain information in sleep mode?

texts: I'm trying to write a long term timer function on an attiny85 and currently I'm using a counter. I'm experimenting using sleep mode as detailed here. I'm wondering if the chip "retains" information in sleep mode. For instance if I increment a variable and then go into sleep mode, will that variable be changed when the chip wakes again?


texts:
I have two questions here for how to connect the oscillator to a microcontroller (SPC584b):

How can I determine the values of the capacitors?
What is the need of SB2 & SB3?


texts: Negative gate transients on high side half bridge FET

texts:
I am trying to simulate a half bridge for a 3 phase motor driver.

When my high side FET transitions off, during the dead time, the switch node voltage is 25V. I would expect this voltage to be a diode drop below ground as the body diode of the low side FET should supply the current to the inductive load in the following loop:

When the low side fet transitions on, the sudden dv/dt caused by the switch node transitioning from ~25V to ~0V appears to couple to the high side FET gate through Cgs and cause a large negative transient.

I'm trying to understand why the switch node is staying at 25V after the high side FET turns off, and how to resolve the dv/dt that is causing my high side FET gate transient.
Currently I suspect my low side FET snubber cap is holding up the switch node at 25V, but not sure how to fix the negative voltage transient at the high side gate.
Edit: Updated my circuit after fixing the items pointed out in the comments, still getting large negative transients on my low side gate

I've tried slowing down the turn-on of the high side FET, making the snubber cap on the low side larger.


texts: Using a capacitor instead of a coil for wireless charging?

texts:
This might sound like a stupid question, but I'm kinda interested in a detailed explanation.

So while inductive charging is rather ubiquitous, things like electric toothbrushes and Qi chargers come to mind, as well as to a lesser extent, wireless charging pads for cars, the are all inductive charging systems, basically forming half of a transformer each (the charger is one half, the charged device the other half).

But would it be technically possible to make such a charging setup, using a large capacitor?

I.e. having an AC source connected to a large plate, forming one half of a large capacitor. The charged device would then form the other half of the capacitor.

I understand the distances would have to be rather small, but in cases like Qi chargers, the're right on top of each other anyway. Also, the dielectric properties of the materials between the two conductive plates, would obviously play a role.

But from a purely engineering perspective, why is it a bad idea? One problem I can come up with, is using very high frequencies. The charger side of the capacitor would essentially be an antenna, with the sizes of a smart phone, that would mean frequencies in the 500MHz-3GHz range. I assume it'd be simply too complicated to use a signal generator at these frequencies to send sizeable amounts of power?


texts: Implication chart method for state reduction

texts:
I'm not understanding implication charts to reduce states for Mealy and Moore machines. I'm looking at an example from berkley

I was able to construct the table and then also eliminate the ones based on that output(here's the one from the site since you can't see my whiteboard)

The thing is, I don't understand how they got to the next step.

How did they decide to eliminate those states? Following the steps, I wound up eliminating several steps they kept, such as a and d, since c and e are clearly not the same.

What am I missing?


texts: Circuit to turn microcontroller on when reed switch state changes (to monitor door lock state)

texts:
I'd like to build a circuit that provides power to a microcontroller (ESP8266 in this instance) when a reed switch is changed from closed to open AND when changed from open to closed.

This is to be used in a circuit that will monitor the state of a deadbolt lock. I'm planning on attaching a magnet to the end of the bolt and putting a reed switch inside the strike box with enamelled wire running out to the ESP8266 that will be discreetly mounted on the wall nearby. The circuit will run on batteries as running power to the lock location is not practical (nor will it have a high enough WAF to get approval).

When the lock is closed it will open the reed switch and when it is open it will close the reed switch (or the other way around, I'm not fussed whether the reed switch is NO or NC).

When someone locks the lock I'd like the circuit to provide power to the ESP8266 so it can connect to wifi and send a message to the automation server recording that the lock was closed and then power itself down (ideally to a zero current draw state).

Then when someone unlocks the lock I'd like the same thing to happen, albeit that the message will be different, but I'll handle that in code, obviously.

I've researched soft latching power circuits but they only seem to work when momentary switches are pressed. Here's an example from EEVBlog:

https://www.youtube.com/watch?v=Foc9R0dC2iI

Here are another two examples of similar one-sided circuits:

https://randomnerdtutorials.com/latching-power-switch-circuit-auto-power-off-circuit-esp32-esp8266-arduino/

https://www.instructables.com/id/LEIDS-Low-Energy-IOT-Door-Sensor/

This is a similar question but seems to rely on there being constant power available at the lock location so not good for my application:

How to create a locked door detector?

This also seems to be asking a similar question but I can't fathom the answer (and there isn't a final diagram showing how the XOR gate is hooked up to the switch and the microcontroller):

I need a switch that not only detects open/close, but also sends a pulse to wake up an ESP8266 whenever the (debounced) state changes

I've also though about maybe having the ESP8266 in a deepsleep-wake cycle every 5 mins or so and just reporting the state of the reed switch but this would mean the batteries only last a few months and I'd like it to last much longer (>1 yr). The other problem with that approach is that I may have to wait up to 5 mins to know whether the lock is open or closed - often I drive away from the house and within 1 or 2 minutes want to check if I locked the lock on the way out so being able to check instantly would be very helpful.

I also wonder if it could be done using two reed switches, one NO and one NC to somehow trigger the system...?

Any help would be greatly appreciated, even if it's to say that I'm asking the impossible!


texts: Why is it necessary to use a voltage divider to bias the base voltage in a common emitter amplifier?

texts:
I have seen different common emitter amplifier designs with either a voltage divider or a simple resistor between the battery and the base.

What would make us choose a voltage divider over a simple resistor?


texts: What's the difference between a monostatic and a colocated radar?

texts: I have heard the two terms thrown around in a somewhat interchangeable manner it seems. Are there any major differences? I haven't gathered that they have a different meaning, but I don't understand why there would be two different words if that were the case, as it seems authors choose one over the other somewhat randomly.


texts:
I am designing a keypad in VHDL. Everything works fine when only a single key is pressed. I'm scanning each column for a key press in a state machine and when no key is pressed, which is the condition pin4pin6pin7pin2 = "0000" I switch to next state for scanning the next column. Thus I set the columns pin3pin1pin5 sequentially to "001", "010" and "100".

While scanning pin3pin1pin5 as "001" and if pin4pin6pin7pin2 is "0100" then simply "9" is pressed. I declare in VHDL pin4pin6pin7pin2 as input and pin3pin1pin5 as output ports. When I press 6 and 9 at the same time pin6 and pin7 are high. The first pressed key is read, the second one is ignored. When I press 3 and 7 at the same time, the first one pressed with few ms before wins and the first key is read, the second key is ignored, pin2 and pin4 are high.

Here is the tricky part. When I press 4 and 6 at the same time, I expect pin7 to be high but it becomes low and pin4pin6pin7pin2 = "0000", which I don't understand how and why. Because "0000" is detected as a no key pressed, the state machine jumps from state to state. While holding 4 and 6 if one pushes and leaves 4 several times, it is detected as 6 pressed several times, which is a big bug. I would be glad if you can help me debug this!

Same thing happens with "1" and "2", same with "7" and "8" only for the keys on the same row. Since this is an ongoing project I can't put my VHDL code online :( I would be glad if you can give me tips to overcome this!

Below, Im not uploading my code to the board, no code is running. Connecting Pin5 to ground, a single press on 1,2,4,5,7,8,*,0 does not turn Pin3 LED on but if Im pressing 6 and then 4 at the same time Pin3 LED is on and Pin7 LED is still on, but when my code is running this doesn't happen. Maybe I connected something wrong and luckily Pin7 is on, I don't know...

Below is the schematics of the keypad board:


texts: High Speed Signal on Large Circular Ring

texts:
It's frequently communicated that when working with signals in the Ghz range, routing is extremely important to signal integrity. Pretty much any inclusion of unnecessary stubs is out of the question, traces must be length matched to some fraction of the wavelength, vias backdrilled, etc.

That being said, I've been tasked with an unconventional goal of creating a high speed (1.5Ghz) signal interface along a large circular ring (e.g. a slip ring) of a maximum 3 inches in circumference. The signal will be introduced at one random point in the ring and picked up at a fixed location at another place in the ring.

Specifically, I'm not quite too sure what the implications are / if it is possible to operate at that level of speed given the self induced jitter from the phase shift. Assuming the following, are there any opinions out there on if this is possible or not? If so, what additional mitigation measures can be taken in this particular scenario?

Annular ring impedance matching to termination
Gold on gold contact to introduce signal
EQ/DI/OS SC IC (ReDriver) immediately after for insertion loss
Clocked Retimer eventually after to hopefully save the signal


texts: How to match the length of wire for a symmetrical circuit?

texts:
I am new to my current job and one design inherited from my predecessor was as follows. I am wondering if this is the best practice to make a symmetrical circuit.

I was told that the two wires (R+ and R-) should keep the same length to make a symmetrical circuit. To do that, the designer put some turns on the layout. It looks weird to me, but wondering if this is a common practice. The frequency in the circuit is up to 1.5GHz.


texts: Verilog - variable number of inputs/outputs

texts:
Is there a way in verilog to do the following? I have a variable number of FIFOs (1 to 4) created with a generate statement inside of a module

pseudocode:

module()
    generate( for i to NUM_FIFOS )
        FIFO fifoI( args )

What I want to do is have the read data from these FIFOs as outputs of the entire module. Is there a way to have a variable number of output?

e.g.

module(
    generate for( i = 0 to NUM_FIFOS )
        output FIFO_dataI
    )

Thanks for the help!


texts:
I have an AQZ204 AC/DC type solid state relay AQZA204 datasheet

I'm using 31.5 volt DC supply, with a series 4.7k Ohm Resistor to the input LED of the relay.

The data sheet is a little confusing to me, it saids the LED max dropout voltage is 1.5V so I calculated around 6.38mA forward current for the LED:

31.5VDC - 1.5Leddrop = 30VDC/4700 = 6.38mA

I'm confused by the IFon current being 3mA max?

Basically I want to calculate the minimum  supply voltage required to turn the relay on

and the minimum supply voltage required to turn the relay off

So I can test the relays to see if they are in spec.


texts: Use momentary switch to switch between three devices

texts: I need a solution to use one momentary switch to switch between modes on a pump. Off (NC) | Low | High. What I mean is you push the pushbutton once to turns pump on low, push it again for high and again for off (NC).  Additionally on low I'd really like the switch light to flash slow, and on high the switch light to flash fast. I've seen it done with Raspberry pi (https://www.youtube.com/watch?v=LOwnG5Vhzcs) but would like a simpler (maybe relay) option.


texts: How to detect a (very) small change in the position of a needle?

texts:
I am very sorry if my question is too basic (or odd), but I do not know anything about electrical engineering.

I would like to mimic the motion-sensing filiform hairs in spiders and insects:

The hair is loosely suspended in a socket, and as it moves, it stimulates a nerve. Basically, it comes down to detecting a very small change in the position of a needle.

My intention would be to use the results to measure air flow in an HVAC vent, so a carpet of these hairs would be dropped into a vent, which would then give readings on flow across the surface.

The constraints would be rough handling (it would be rolled/unrolled, bent, etc). It should also be easy to clean.

My ideal answer would be a link to a device, tool, or circuit that does a very similar thing, or a (very simple) explanation of what you would do to mimic this measurement. I am trying to find the most cost-effective means possible.

Thank you!

PS. I've already looked at this question, but I do not understand the diagrams.

PPS. Here is an article on the biology.


texts:
Just need some help understanding what's happening in removing the DC offset from two band-pass filters.

VG has a value of 4.5V. When I added in the virtual ground the circuit had an offset of 4.5V at the Out and Out2 nodes. I added in capacitors C7 and C8 at 1\$\mu\$F understanding that it will block the DC signal. This worked for the node at Out but not Out2. Later I saw a similar problem where the solution was to put a resistor between the output and opamp which worked but I do not understand why the resistor is needed and why Out didn't need one but Out2 did.

The resistor that was added was R7.


texts: What does an ideal phase response look like for a single port SAW resonator?

texts:
I've been struggling to find an example of an ideal phase response for a single port SAW resonator. In particular, I'm looking for a graph similar to this one:

which shows the admittance/conductance and phase response of a BAW resonator, but for a SAW resonator. Can I expect the same type of response out of a SAW resonator as that shown in the graph above, or will it be different? Forgive me if this is a basic question, I have a textbook on SAW devices in front of me but can't for the life of me find anything about the phase response in it (or in my extensive Google searches for that matter). Any help would be greatly appreciated!


texts:
Can you draw 12mA from a CR2032 (or RL44) cell for long time? The data sheets says ~240mAH means about 24 hours to 2V, but it says that for draw less than 1mA typical...

And if there is no max, can I calculate the capacity — mAH, as a const, or does it change according to the current draw?

Does pulses draw is better or worse for capacity?

Is there a "home" (a place where you put that battery into such as other cells have)?


texts: Strange behavior in VHDL design (randomly incrementing values)

texts:
I have a fairly simple VHDL design that looks like the following:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity myCode is
    port (
        input_clock : in std_logic;
        do_increment : in std_logic;
        counter_out : out std_logic_vector(4 downto 0)
    );
end myCode;

architecture Behavioral of myCode is

signal internal_counter : unsigned (4 downto 0 ) := (others => '0');
signal do_increment_delay : std_logic := '0';

begin

counter_out <= std_logic_vector(internal_counter);

process(input_clock)
begin
    if(rising_edge(input_clock)) then
        do_increment_delay <= do_increment;
        if( (do_increment = '1') and (do_increment_delay = '0') ) then
            internal_counter <= 1 + internal_counter;
        end if;
    end if;
end process;
end Behavioral;

The goal is to increment the counter_out by 1 on the rising edge of "do_increment" signal only.

When I look at my running design in ChipScope (running on Spartan-6 FPGA), I see that the code is doing what is expected:

However, during periods of time when both do_increment and do_increment_delay are low, the counter begins to increase on its own:

There is no other assignment statement to counter_out anywhere.. the chipscope clock is the same one used as the input_clock to myCode. I have scoped out the do_increment physical signal into the FPGA and it is not noisy.

Any ideas?


texts: Activation of multiple LEDs with one or several transistors

texts:
I have to activate four LEDs at the same time when the signal varies from 0 V to 5 V. I still have not defined the transistor I will use, but before that I would like to know the best way to do this, with schematic 1 or with schematic 2: Activate all the LEDs with a single transistor or each LED to be activated by a dedicated transistor.

I know I should consider the current that will pass between collector and sender to determine which of the two methods to use, but I would like to know which one is the most correct.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts: Why is the output signal greater than the input signal in this voltage follower circuit?

texts:
I have implemented this circuit on my breadboard.
The voltage waveform at point A and B in the circuit attached below should be equal because it's a voltage follower, but in my case, after implementing on the breadboard I am getting higher output voltage (Point B) than the input voltage (Point A).
I have also attached the input waveform and the output waveform.

Can anyone tell me why this phenomenon is happening?


texts: Searching for an analog circuit solution, where an output voltage is incremented or decremented based on an input

texts:
So I have an interesting request that I've searched the internet for and have not been able to find, or been able to come up with in my head.

I have a circuit with a feedback loop that is meant to control a MOSFET.  The feedback loop has a difference amplifier that outputs the difference between the current output and the desired output.  Based on this, the voltage to the gate of the MOSFET should change.

In other words if the output of the system is currently 11V, and the desired output is 12V, the difference amplifier has an output of 1V, and this 1V output should somehow signal that the MOSFET gate voltage needs to increase.  Similarly, if the current output is 13V, the difference amplifier would have an output of -1V, and should signal that the MOSFET gate voltage needs to decrease.

I initially tried hooking the feedback output from the difference amplifier directly, but quickly realized that wouldn't work.

Rather, I need a circuit where a + voltage causes a constant voltage increment until the feedback reaches 0, or a - voltage causes a constant voltage decrement until the feedback reaches 0.  So the feedback should be a sort of specification of the rate of change to the base voltage.

In a nutshell, this is what I'm referring to:

My initial guess is that this might have to include a non-inverting amplifier, or even just a comparator comparing the feedback signal to ground, and charging of a capacitor that powers the base voltage to the MOSFET.

Edit

Came up with something, looks like this works fairly well. Still open to better suggestions though.


texts: How to capture the I2S signal via Raspberry Pi Zero?

texts: I would like to capture the I2S data from ADC CS5340 by raspberry Pi zero, but I could not find relevant I2S API to use in raspberry pi zero. Could anyone help me on this? Thanks!


texts: Is it necessary to have a finite state machine for every filter you write in VHDL?

texts: I have recently coded a filter in VHDL to be synthesized for an FPGA and I did it using the conventional method where you first design the finite state machine(FSM) and then implement it in your code. But I realized that when I reduced the number of states in the FSM by combining a few states, the filter worked much faster. So, in an attempt to maximize the speed of computation, if I just write the entire filter inside a process so that all the statements get executed sequentially, will it affect the computation in any way?


texts: Battery Charge and Discharge time for constant voltage charge battery, and how to know if its fully charged

texts:
In my Project I used below battery and a battery back SMPS.

Battery
Type:- Sealed Lead acid , Volt:- 12V, Ah:-7AH
Charge parameters:-
Constant voltage charge with voltage regulation
Standby use 13.6V-13.8V
Cycle use 14.1V-14.4V
Max initial current 1.4A

SMPS
Input 85Vac to 264Vac , 50Hz
Ouput :- 13.8V DC
Below image from SMPS datasheet

I read the SMPS datasheet , but there is no information of charging and discharging of battery timing.

Load
I have connected a load of 20W at +v and -V terminal.

Q 1) I setup everything, Connected the battery, put a multi-meter across battery terminal, voltage on display slowly slowly increasing. At what level I know that my battery is fully charged and I should disconnected it to being overcharged.

Q 2) About Battery Backup time.

 a) If we use formula  Tbck= (Vout* AH)/(op Watt) , i got 4.2hrs. Is it    Right calculation

 b) If I use other formula with Battery spec (see attached image)

Consider 3HR rating of 5.2AH.   Current= 5.2AH/3HR = 1.73A current it can supply till 3 Hrs. ( right ??) so after 3 Hrs how much voltage of battery will be
0 volt or 10.5V. Since my SMPS cut the battery if its lower than 10.5V.

Q 3) Charging time of battery

Since no information given in SMPS datasheet about charging current or else, can not figure out about charging time of battery.
  a) Battery is constant voltage regulation charge type and SMPS is charging the battery with 13.8V, then any method to calculate the charging time of battery.


texts: MOSFET mechanism of failure: was it the heat?

texts:
I am debugging a failed MOSFET (IRF6662), and in the process of doing so, am having difficulty understanding fully the thermal behaviour of the FETs. Two FETs used for DC switching both failed short independently (2 Ω short over S-D, and lower-than-usual ~1 kΩ resistances S-G and D-G). These failed when I turned the each FET on into a substantial load (34 V into 9 Ω an 1 mF of capacitance). These FETs are driven by a switch controller (LT4363) that has a soft-start feature, so the load voltage ramps up linearly over about 100 ms.

I believe what happened was thermal damage due to the higher-than-normal power generation into the FET when the switch controller held the FET in ohmic regions before it switched on fully. I estimate that an average power of 20 W was dissipated in that 100 ms period, concentrated mostly into the middle half of that time. Using a thermal resistance junction-to-ambient of 5°C/W (from Fig3, the transient impedance plot for a 100 ms pulse), I get a Tj temperature rise of 10°C, well within acceptable bounds. So, if I have understood this right, it doesn't look like a simple case of overheating. But, does this thermal calculation make sense in this case?

Another possibility is thermal instability. Looking at the SOA of the FET, and estimating the I-V curve across the 100 ms turn-on period, I get this:

It looks like I am venturing out-of-limits for a period of time, crossing not the max power or max voltage limits, but a "thermal instability limit". But it's unclear if my transient violation of this limit is dangerous, or if this violation is likely to cause a FET failure like I have seen. In general, could such a transient incursion over the thermal instability line of a FET cause it to become damaged like this?

Lastly, these (transient exceeding max junction temperature and thermal instability violation) are the only two thermal damage methods I can see being relevant. I'm not driving the gate anywhere near fast enough for dV/dt problems, nor am I approaching the avalanche breakdown voltage. Are there any other damage mechanisms that might give these same shorting symptoms?


texts: Capacitance and battery and no resistor and time

texts: I already know the 't=RC' . But what happens if I start charging a capacitor via a same voltage battery? When will it be fully charged?


texts: How twitchy are larger digital servo motors?

texts:
In my servo-driven pen-plotter project, I have been experimenting with various different servos to discover more about their characteristics.

In practice I have found that:

analog micro servo motors work well and give good results, as you can see
comparable digital micro servo models are useless for the purposes

This is because the masses attached to them cause digital motors to oscillate uncontrollably at the slightest provocation (because the motors are both twitchy, and not very powerful).

I'd like to try some larger digital motors, but I don't want to spend money unnecessarily if I'm only going to discover that they too are unsuitable for the purpose. I hope that someone else with more experience of servo motors in general can give me an informed judgement.

How much less susceptible to oscillation are larger digital motors? Given the arrangement illustrated, am I likely to discover that they exhibit the same sort of behaviour?


texts: Determining the ramp-up speed for a stepper motor with its drive system

texts:
How can the required ramp-up speed for a stepper motor which is attached to its drive system be determined?

Given that a stepper motor requires ramping-up to full velocity, and that ramp speed must be slow enough so that the motor doesn't simply vibrate in place, is there a known method for determining the ramp-up speed?


texts:
Let’s say we have the noise figure F of a system of devices. We also have the bandwidth improvement coefficient ( as defined by my teacher ) $$BI=10log(\frac{B_{in}}{B_{out}})$$ where B1 is the bandwidth at the input and B2 the bandwidth at the output of the system.
Having these two, my teacher claims that the following stands : $$SNR_{out}=SNR_{in} - F + BI$$

Everything in the expression above is in decibels.

I really don’t understand why the BI is in the equation. Even Wikipedia’s definition of noise figure doesn’t include that term.

The equation is supposedly derived from the definition of thermal noise : $$N_{th}(dBm)=-174 dBm +10logB_1$$ where B is the bandwidth and the definition of noise figure as the amount of noise, produced by a device,which is above the thermal noise : $$N(dBm)=-174dBm +10logB_2+F(dB)$$

I can see that $$N-N_{th}=-F(dB)+ BI(dB)$$
This is as far as I can get .. Moreover, if BI is greater than F , then SNR_out will be greater than SNR_in. Is that even possible ?

Note : This is all based on an exercise on superheterodyne receiver.


texts: Trouble with communicating with an AD5292

texts:
I have an AD5292 connected to an ATXMEGA's D port SPI and am supposed to communicate with it. Alas, it doesn't react to my commands.

(Instead of a "real" pullup resistor, I have activated the ATXmega's internal pullups, but at low speeds (about 500 kHz), at least that seems to work.)

According to its data sheet, I am supposed to have CPOL = 0, CPHA = 1 - which means SPI mode 1. Trying modes 0 and 2, I get the data which I put in back, but shifted by 1 bit. Modes 1 and 3 give me the same data that I put in.

As said, I get the same data back from the device that I sent to it, even if I issue read commands (read RDAC register, read memory, read status register), and the device ignores my requests to change the resistance. So it seems to ignore all commands.

I already hat the idea that I do something wrong with the SYNC/CS line, but if I omit that line, the device only gives me back 0 bits, so probably the SYNC line is activated correctly as well.

Besides the communication problems, I notice that the device constantly holds the RDY pin LOW.

These two problems are probably related to each other. I think that if I fix the RDY line problem, the other one is gone as well. (Resp.: if I fix their common root cause, both are g0one.) But I cannot figure why the device would hold RDY low all the time.

Did anyone of you experience the same problem?


texts:
First off I do apologize for my ignorance,
I know very little on the topic so please be patient.

I have one of these that are broken
http://www.smartliving.com.au/z-wave-in-line-dimmer.html

Its a Z-Wave dimmer that plugs into a lamp
It enabled remote switching and dimming of a lamp plugged into it
The micro-electronics portion of the circuit is fine and I can switch the device on and off remotely (Based on the onboard LED correctly showing status)
I did a visual inspection on the circuit and cant see anything obvious wrong
All the capacitors appear fine to me

At this stage I believe its the high voltage portion of the circuit that has a problem.

What is this coil cylindrical thing on the board?
How do I test it with a multi meter?
I tested the BT139 600e triac, if I do a continuity test across the first and third leg I get a closed circuit (My MM beeps), could this be my issue?
Any other common problems I should check to troubleshoot a dimmer?

Any help will be GREATLY appreciated!


texts: reduce power consumption on this audio mixer

texts:
I'm wondering if you can reduce the mA consumed by this discrete audio mixer (on both +12V and -6V) by changing the resistors values, but keeping the same functionality (same gain, same asymmetrical clipping levels).

Also, as second question, is it possible to power this from +10V instead of +12V, keeping again the clipping levels unaltered? I guess not, since it would clip earlier, but what if you use -8V instead of -6V to balance that?


texts:
My textbook, Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk, says the following in section 2.3.1 The Mechanisms of Voltage:

  In regard to potential energies of free electrons within the conductors leading to and from the battery, we assume all electrons within the same conductor have the same potential energy. This assumes that there is no voltage difference between points in the same conductor. For example, if you take a voltmeter and place it between any two points of a single conductor, it will measure 0 V. (See Fig. 2.8.) For practical purposes, we accept this as true. However, in reality it isn't. There is a slight voltage drop through a conductor, and if we had a voltmeter that was extremely accurate we might measure a voltage drop of 0.00001 V or so, depending on the length of the conductor, current flow, and conductor material type. This is attributed to internal resistance within conductors - a topic we'll cover in a moment.

I can't help but wonder if the authors are understating the potential for voltage drop through a conductor. Their estimation of a 0.00001 V drop seems reasonable for a relatively small electrical circuit, but what about for large-scale power systems, where the conductor may span many miles (say, an undersea cable, an electrical grid (although, I assume that electrical grids have hardware in place to "boost" the voltage between power plants and delivery destinations), a solar farm in the desert, etc.)? In my, perhaps naive, mind, I wonder if the voltage drop would not just be minor in such situations, but significant enough to cause practical problems?

I would appreciate clarification on this. Thank you.


texts: Do I need a fork terminal to install #8 into an 38660 Molex Barrier Strip?

texts:
Can I strip a half inch of wire from a #8 cable and screw directly into a 38660 Molex connector? Or do I need to buy a spade terminal. This is for an AC connection to the back of a DC power supply, there are not clear instructions on the data sheet.
https://www.molex.com/pdm_docs/sd/386608802_sd.pdf

From: https://www.digikey.com/product-detail/en/molex/0386608802/WM4395-ND/2421327


texts: Changing the resistor to be in front or behind an LED doesn't affect brightness?

texts:
Note: I am very new to the more advanced side of electricity. I do not have a firm grasp on the exact mechanics.

Lets say I have an example circuit:

5V Power Supply -> LED -> Resistor -> Ground

Now the LED is receiving 20ma and 5V.
If I were to switch the LED and the resistor however, the LED should receive less voltage but the same current, so wouldn't it be dimmer?
Or would it receive the same voltage?

I've looked at these two threads and their answer doesn't help.
Why doesn't it matter if a resistor is before or behind an LED wrt voltage drop?
Why does a resistor need to be on the anode of an LED?


texts: I wanted to do a little project with the µC mentioned above (TQFP-44 package). I looked into the datasheet, obviously. But there are multiple names for the pins which aren´t the voltage supply. How can I determine how the pins are labeled? Or does this depend upon the application of the µC?


texts: What's the standard procedure of DDR4 training?

texts:
I have a question about DDR4 training sequence, and hope someone can give me some information.

As I know, there will be training sequence at system boot.
(In my system, it's called 1D/2D training, I'm not sure if that's a standard term or it's the specific term for this controller).

My understanding is, the controller will get a "working condition" through this training process (the working condition is a suitable Vref and RD/WR timing).

Is that a standard procedure for all the DDR4 DIMM?

How do I train a DDR4 memory module?


texts:
I made a switching power supply (input: 24VDC, output: +-15Vdc) for LEM (current sensor). Noises of the power supply caused the output of LEM to become a bad waveform, but I don't know how to eliminate noises of switching power supply that show on the below picture.

Can anyone help me ?


texts: Resistors to make an 74hcxx IC behave like a 74hctxx IC

texts:
I made a circuit that is supposed to detect when all 8 output lines are logic high.  I connected the inputs of a 74HC30 (8-input NAND) to the data lines of an AT28C256 (ROM). After a while, I checked the datasheet of both of these devices, and it states that for AT28C256:

  output low voltage max: 0.45V
  output high voltage min: 2.4V

And for 74HC30, it states:

  high level input voltage min: about 3.15V
  low level input voltage max: about 1.8V

For 74HCT30, it states:

  high level input voltage min: 2V
  low level input voltage max: 0.8V

I've already built the circuit with everything soldered in place. Rather than go through 1/3 a spool of solder wick and replacing all my 74HC's with 74HCT's, would I be able to add pull-up or pull-down resistors to all the inputs of the 74HC30 to make it function like a 74HCT30 without using excessive current?


texts: Can I use conductive silicone for anything I could use solder for?

texts:
I got my hands on a big tube of conductive silicone. I've never heard of it before, but my first thought was, "Is this just basically wire in a tube?" Has anyone ever used this before? Can you just apply it as a low heat solder? The people I got it from said this stuff is kinda expensive, but I got it since they were just going to get rid of it (at cost, so they were glad to let me have it). Plus it is expired (does silicone expire?).

Anyway, anyone have any experience using the stuff?


texts:
I have this project listen below and im not sure where to start maybe someone can give me a few pointers or perhaps point me in the right direction of starting this?
Thanks!!

Input: A, B = octal digits (see representation below); Cin = binary digit

Output: S = octal digit (see representation below); Cout = binary digit

Task: Using binary FAs, design a circuit that acts as an octal FA. More specifically,
this circuit would input the two octal digits A, B, convert them into binary numbers, add
them using only binary FAs, convert the binary result back to octal, and output the sum as
an octal digit, and the binary carry out.

Input/Output binary representation of octal digits

Every octal digit will be represented using the following 8-bit binary representation:

Octal     8-bit Input Lines:

Digit:     0  1  2  3  4  5  6  7
0              1  0  0  0  0  0  0  0
1            0  1  0  0  0  0  0  0
2            0  0  1  0  0  0  0  0
3            0  0  0  1  0  0  0  0
4            0  0  0  0  1  0  0  0
5            0  0  0  0  0  1  0  0
6            0  0  0  0  0  0  1  0
7            0  0  0  0  0  0  0  1

You  are  required  to  design  the  circuit  in  a  structured  way.


texts: What options are there for programming MCU's in production?

texts:
For my Super OSD project I'm going to need to program large batches of MCU's, probably about 10-15 boards an hour. I could just use my trusty PICkit 2 to program them (there are two - maybe three - on each board) but it would be very laborious to load each file (up to 128KB and 256KB in size), hit program, and repeat for each MCU, and probably wouldn't allow me to meet my target speed. Also, the MCU's are surface mount, so I have to have headers on the board to allow this. Ideally, I'd like to remove these headers, but it may not be an option.

So what options are there for mass programming of MCU's - are there faster ways to do it? I'm kind of on a budget of less than $100 USD, so things like Microchip's MPLAB PM3 at $895 USD, while nice, wouldn't be an option.

I'm dealing with PIC microcontrollers of various types. There's a PIC16F887, PIC24FJ64GA002 and dsPIC33FJ128GP802. However, I am also interested in options for AT32 and STM32 processors, as I may also be using them.

Please note, I'm not currently considering ordering chips from the manufacturers pre-programmed because the software may change by the time the chips arrive, and because of the additional cost involved.


texts: NMOS saturation mode: why is there no channel?

texts:
I have a question about the saturation mode. The cross-section of an NMOS transistor in saturation mode is usually drawn like this:

But it seems to me that there can be no current from source to drain in this case (because there is no contact between the channel and the drain). From the diagram that plots V_DS against I_D, it can be seen that in saturation mode, there is a current (it just doesn't increase when we increase V_DS).

So what is going on in saturation mode?


texts: driving a 5v LCD with a 3.3v atmega328p microcontroller

texts:
Am using adafruit (American hobbyist electronics components retailer) breakout for the max31850 thermocouple amplifier who's data line isn't 5v tolerant. Therefore I want to power my atmega328P @ 12mhz 3.3v. I have been told this is the optimum speed for a 3.3v power rail.

THe lcd am using to display the temperature is unfortunately a 5v lcd I believe since I tried powering it from 3.3v it didn't even light up. I used a commercial bench supply @ our lab to test this. As soon as I upped the voltage to 5v it lit up the first row. My question is will the 5v on the lcd cause damage to the atmega? MY understanding is current always flows towards lower potential. The difference in voltage can cause a large current to flow right?


texts: Is a 10GHz clock required to drive a 10Gb serial pin?

texts:
I am reading about the 10Gb/s Ethernet PHY for Altera FPGAs (datasheet here). I was impressed to know that, at the hardware level, the 10Gb/s is done serially.

Naively, I would think to do 10Gb/s serially, one needs a 10GHz clock. However, 10GHz seems awefully high for a clock, and the datasheet does not specify a 10GHz clock anywhere.

How is 10Gb/s serial communication done? What clocks drive such transfers?


texts: What is the stuff hardened on an old flyback transformer?

texts:
I am restoring some vintage old Mac computers with the integrated CRT display. These have a flyback transformer on their analog board. Part of this device is some hardened brown/orange material at the top that is solid and crumbly after 30+ years. It seems to have secured the bracket part in place as it passes through the central cylinder part.
Can anyone tell me what this material is/was, what job it was doing, and how to replace/refresh it when the system is intended to go back into use? Thanks!


texts: What is the parasitic resistance due to an IC package in a mosfet? (or any package)

texts: How much resistance does the package of an IC contribute to the paraistic resitance of a circuit? (most applicable to mosfets)


texts: Mosfet Voltage Gain in common-source configuration

texts:
I have some doubts about this so-called transconductance which can be either calculated for BJT or for FET transistors.
As far as I know, since BJTs are current controled devices, its transconductance (gm) differ from the FETs.

BJT's gm=Ic/Vt (Vt -> thermal voltage ~= 25mV at room temperature)

FET's gm= Id/Vgs (Vgs -> Gate-Source Voltage)

My question is: When you design a MOSTFET common-source amplifier and you want to know its gain, do you always need to calculate it's gm first? And if so, how do you start your calculations?

When I look at the datasheet of a MOSFET, the only thing is given related to transconductance is:

Is this helpful for our calculation?

Here's the schematic of the amplifier:

They say the fallowing:
"The gain of this amplifier is determined partly the transconductance of the MOSFET. This depends on the bias point of the circuit, here it averages about 9mA/V. This means that a change in the gate voltage causes a change in the drain current that is 9mA/V times the gate voltage change"

Does this mean that the MOSFET's transconductance is 9mA/V And if so, how did they found out this ?

They even say that " A change in input of 50mV causes a change in drain of voltage of 9mA/V * 50mV * 4000 ohm which is equal to 1.8V". And dividing this 1.8V with the input voltage 50mV will result the gain of this amplifier which is 36. But how did they reach to this calculation?

On the other hand my book says that the voltage gain can be calculated with this formula:

Gain = vd/vgs = (-Rd*id)/Vgs  and we can rewrite this as: Gain = -gm * Rd

So if I compare this formula to the one that they used above, with gm * Vgs * Rd there will be obviously a difference which makes me confused.


texts:
I am working on a system with a microcontroller than controls other microcontrollers, mainly sending commands to the other micros.

I built in a Watchdog Overflow function on the 8051, which basically just puts the device in an endless loop, thus not kicking the watchdog periodically, which then makes it fall over (reset). Like: for(;;)

The way I understand is that overflowing the watchdog in firmware is essentially the same as doing a hardware reset on the micro.

Why do I then get different results when overflowing the watchdog than power cycling the entire unit?

The 8051 is the heart of the unit and controls all the other devices.


texts: How to set the offset for the components name in Eagle schematic?

texts:
I am using Eagle 7.1.0. In the eagle schematic the component name is started by default by 1, 2, 3, …

For example I want to use an offset of 100. Eagle should give the component a name like 101, 102, 103, …

How can I create an offset so that Eagle starts numbering from different value?


texts: Why do so many crystal radios have big coils?

texts:
I've been looking at crystal radios recently, and I noticed that many of them had quite big coils (maybe around 5cm on average from what I can see), but wouldn't they want quite a low value inductor to get the right frequency without using an absolutely miniscule capacitor? I know the size would have been quite useful for tapping, but wouldn't they have still wanted them as small as possible?
These are some of the images I found, they are all modern recreations and kits, but ones made to look like the old ones:

https://steampunk.wonderhowto.com/how-to/complete-guide-build-crystal-radio-plus-they-work-0141117/

https://en.wikipedia.org/wiki/Crystal_radio

hackaday.com/2020/01/28/eric-talks-crystal-radios/

https://www.mtcradio.com/the-pickard-crystal-set-radio-kit/
This is the equation I was using to calculate the frequency:

https://www.elprocus.com/lc-oscillator-circuit-working-and-its-applications/
These were the formulas I was using as a reference for inductors (I know they're air-core, but they showed me that increasing the radius of the coil increases the inductance, which should be the same for a ferrite-core inductor as well)

https://www.allaboutcircuits.com/uploads/articles/round-wire-formula.jpg


texts: PCB contacts for membrane keyboard looks corroded?

texts: One of the keys on my Rigol DS1054Z oscilloscope wasn’t working. I opened up the scope and this is what I found. Is that K5 pad corroded? Other than sanding it is there any other way to restore functionality? I tried cleaning it with IPA and then Acetone but that didn’t work.


texts: Is there a way to have visibility of certain part of Nios II system memory for debug purpose?

texts: To know what value exists at address X one may simply read it using IORD and then send it via JTAG UART to the PC. However, to simplify debug process, is there a way to have visibility of certain addresses at all times where registers of certain peripheral are mapped so debugging is easier?


texts: Why are copper pours called copper pours?

texts: I was adding a ground plane to a PCB layout today, and my curiosity peaked. Virtually every EDA package uses the term "Copper Pour." Why is it called a copper pour? It doesn't really make sense considering the copper is etched away. Is it because the pour fills in all areas that aren't part of the net, or is there some historical reason?


texts: Arduino Uno, HC-06 Bluetooth & RGB LED Strip on the same 9V Power source

texts:
Hello!

I am a complete amateur when it comes to electronics so forgive me for any misconceptions.

I am trying to design a circuit that will power an RGB LED Strip (here depicted by a single RGB LED), an Arduino Uno (Rev 3), and an HC-06 SPP Bluetooth module.

You probably already guessed that i want to control the color of the LED Strip using the SPP Bluetooth protocol on a smartphone / other SPP capable device. In the picture you can see the circuit i have come up with.

I have a few questions:

The HC-06 requires 3.3V to work. Is the Arduino Uno supplying 3.3V on the 3V3 rail when the arduino itself is powered off of a 9V Source? I hear the arduino comes equipped with a voltage regulator, so I think the answer is yes.
Is it a problem that the HC-06 Module running on 3.3V is connected to the shared ground connection of the 9V power source? If i were to use a standalone voltage regulator I would connect it to the GND of output side of the regulator, so just connecting it to a shared ground like this is sounding some alarm bells in my head.
Is the RGB LED as depicted in this picture common cathode or common anode? In chemistry i learned that Cathodes are positive and Anodes are negative. However, in chemistry we talk about the flow of electrons from negative to positive. In electronics lingo, it flows from positive to negative. Does that mean it is common anode in electronics lingo?


texts: Why do we consider DC voltage source as short in AC analysis? There is some explanation in Malvino's book but I am unable to understand, can somebody explain this in a lucid manner?


texts: Can you replace electrolytic capacitors with tantalum ones?

texts:
Due to size constraints on a custom PCB, I have opted out for using the smallest type of electrolytic capacitors (3 mm diameter.) However, capacitors in such a small diameter are almost impossible to find.

If I remember my high school books correctly , tantalum caps are actually a type of electrolytic capacitors just with different purpose and their size to capacitance ratio is much better than the electrolytic ones.

I know that they have other advantages, but my biggest concern is is it possible to just use tantalum capacitors instead of ordinary electrolytic capacitors? The circuit in mind is just an ordinary  amplifier for an electret microphone using a simple LM386.

Edit : Here is the schematic, I am asking for all the electrolytic capacitors.


texts: Can a Tri-State buffer be used with AC signals?

texts:
I'm trying to switch an analog audio line from its given channel to analog ground when a specific line goes low (in this case, the DACs charge pump goes low when it shuts down).

Would a tri-state buffer degrade or in anyway impact the AC signal going from the A side to the Y side?


texts:
Can I supply a higher current than the 100mA the USB port will give simply by connecting an external regulated 5v to the power lines, with a diode in the positive side to isolate it all from the USB internal wiring?

Failing this very simple approach, what circuit could be used instead?


texts:
I have downloaded the lm7905 from this source: https://github.com/kafana/ltspice-misc/blob/master/models/regulators.lib
unfortunately, it seems that the output voltage is 0mV all the time (the green value on the included picture).
I am trying to get -5V as the output. Did any one else have a similar problem? Do you maybe know, how to get it working right? The lm7805 for 5V seems to work fine.


texts: How do I read this relay pinout/schematic?

texts:
I'm trying to understand the way this relay works.  To me it looks like this KUHP-11DT1-12 is a DPDT relay.  Pin 7 is connected to 1 or 4 and pin 9 is connected to 3 or 6 depending on whether the coil is energized or not.

What I cannot figure out from looking at the datasheet or the diagram is which is normally open and which is normally closed.  If I had the part in hand, I could simply ohm it out, but at this point I don't yet have the device.

How can I tell from the datasheet instead of having to ohm it out?

Product Data Sheet


texts: Battery (Li-SOCl) voltage varying with orientation

texts:
We are using this 3.6V Lithium battery (ER14505) to power the micro controller circuit in one of our devices. The device is capable of reporting the battery level. Since the controllers brown-out threshold is at 2.7V we use the range from 2.9V-3.5V to report 0-100% (battery should be replaced @0%).

While testing the device, we noticed some sporadic drops in the range of 20-40% that we could not explain. During our investigation, we noticed that the battery voltage varies up to 200mV depending on the orientation of the device!

So we grabbed a single battery and a multimeter and did some tests:

With no load, the voltage stays the same
With 150 Ohm load (22mA@3.3V), we were able to confirm that the voltage is changing nearly 200mV from best case to worst case orientation
"Fresh" batteries are not affected as much as cells that have be in use for some time (still about 3.6V with no load)

I tried Google to gather some information regarding this phenomena but wasn't able to come up with something useful.

Does anyone have information about what exactly is happening, what types of batteries are affected or if we are missing something obvious?


texts:
I have a little veroboard project due couple of days from now and this is my first time encountering veroboard. I have previously worked with breadboards and I understand how pins are connected in those.

My question is, does this veroboard have rails (where multiple pins are connected) or is every pin is individual?

I have tried looking it up on google, but couldnt find anything that would answer my question. I saw stripboards where whole row is connected but the back of those boards looked different from what I have.

Sorry for asking such a silly question and thank you


texts: uncertainty of level measurement variation with frequency response

texts: This is a typical extract from a spectrum analyzer data sheet.I want to know the reason behind the increasing uncertainty of level measurement with frequency response specification.


texts: Two phototransistors in parallel don't have the impedance I would expect

texts:
I have two phototransistors. If I measure the impedance (what I understand to be essentially the resistance of anything that's not a resistor) across just one of the phototransistors, then I measure around 235K. I've checked that they both measure the same.

But if I then put the phototransistors in parallel, then I measure 36k.

My understanding is that if I have two of the same impedances in parallel then they should measure as half the impedance, which should be around 112K not 36K.

The light conditions are not changing in the room. I am measuring with the red lead on the flat side (emitter) and the black on the collector. Can this really be happening?


texts: Can I use gryometers and accelerometers to map the movement of a human arm and then apply it on a robot? The idea that I have is to collect the data from multiple sensors using Raspberry Pi and transmit over to another module via Bluetooth or local WiFi, there the data is translated back and used to drive motors in the robot to mimic basic movements such as walking or flexing of arms. Can the same also be achieved using arduino or FPGA boards?


texts: Two wires for both digital data transmission and energy supply at the same time / Used anywhere?

texts:
Are there any real-life examples for connecting sensors or embedded systems using just two wires that are simultaneously used for both for the energy supply and digital data transmission?
I'm particularly interested in cases in which the sender has to store energy to remain operable (so unlike when using phantom power for microphones, which provide an analog signal anyway).
For instance, the following sketch shows a sender connected to a receiver using a potentially  long two-wire connection that is used for both supplying the sender with energy and for data transmission. The data line is pulled up to 5 Volt by a pull-up resistor, and the sender can cause a logical 0 to the transmission line by temporarily closing the connection between the two lines. However, it can only send short bursts of data, as it must not deplete its capacitor before the transmission is over. The overall energy consumption of the sender is also quite limited in this way.


texts: A good circuit for a large number of push button inputs?

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I'm planning to build a kid-friendly "universal remote" so the kids can turn on and off a myriad of IR-controlled devices with one or two easy presses...

The remote is going to have maybe 20 big chunky buttons which, when pressed, with send the multiple IR signals to all the necessary devices to, say, turn on kids channel, set up the Wii, etc, etc...

Most of the buttons will be laid out in a grid pattern, but some might be used for up/down/left/right, enter, etc....

I'll use an Arduino Pro Mini or Uno as the uC.

Are there any clever ways to wire up these buttons? A grid-type circuit? Analog inputs with different resistors between each button? An IC that'll make the job easy?


texts: Why both voltage and mAh are mentioned in batteries?

texts: If battery is a voltage source then why current is mentioned ? The current depends on the resistance in the circuit right? Then how can a battery give mAh as well as voltage?


texts: Labview inverse Fourier transform: Why can't I visualize Gibb's effect (or ringing)?

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I am studying electrical engineering and have an assignment which I have been working on for couple weeks, but can't solve.
I have a discontinuous function as shown below and applied a FFT on it, which can be seen on the right.
On the bottom right corner is the inverse FFT plot in order to visualize the Gibb's effect, but I am not able to see it.
Why isn't the Gibb's effect showing up in this case?


texts: Full wave doubler difference and connection of neutral and phase

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I'm testing a circuit for creating am unregulated "HV"DC source.
The circuit is like this:

simulate this circuit – Schematic created using CircuitLab

The example I'm using uses a Variac with 120V. I'm limited to the mains supply in Europe of 230V.
The description in the example uses 1500uF caps, I'm using 220uF caps since I don't have any higher.

Using the 120VAC of the transformer, the example circuit outputs 370VDC.
Me, using 230VAC get 330VDC from my circuit between 1 and 2.

A couple of things are still unclear to me.

What is causing the difference between the outputs of both circuits? Is it merely the difference between capacitors? I would expect 240VDC and 500VDC respectively (minus some voltage drop) as output. Strangely, the polarity is also reversed as I expected. I would expect line 1 to be positive, 2 to be negative, but I have to use my meters positive probe on 2 and negative probe on 1 to read a positive voltage.

Secondly, is it required to connect the AC neutral between the caps?
My knowledge of AC is limited and I'm trying to learn it, but although with AC the voltage is alternating, I would expect the neutral carrying the near-earth potential to be negative for cap 1 and positive for cap 2, and reversing this polarity to make the caps puff or in the worst case explode.