texts: Can I change op-amp supply voltage without affecting circuit behaviour

texts:
I am working on an audio project which is based upon various sections of several different schematics from various old musical instruments.
I want to make a test board that has multiple different active filter and eq circuits that I have pulled from the old schematics. So that I can play around and compare them.

In many cases, these schematics are built around the same op-amps, or filter ICs (vintage SSM/CEM filter ics) but the bi-polar supply voltages to these ics vary from product to product. Some operate on +/- 12V some on +/-15V I even have one that works on +/-18V.

Obviously, it gets more complicated to have multiple different voltages on my board, so my question is, can I standardise the bi-polar supply to all circuits without it changing the characteristics or frequency response, or would the complete circuits need to be rescaled?

If the latter is true, where do I even start?

thank you


texts: How to create a buck-boost converter with a low-voltage cutoff

texts:
Hello i would i am in need of a constant voltage regulator to power my motors, as voltage will affect the motors rpm. Although i could compensate via software, i would like to add a hardware deterrence.

My setup would be:

a 7.4 volt nominal supply. This is from 2 18350 li-ions so 8.4v at full charge and 6.8v
4 separate motors that at peak efficiency consumes 0.5A at 7v

My target features are

output current of 1A to 2A ( i could always use 2 or 4 if it has to be, of the same circuit)
can output voltage from atleast  6v - 9v
can be made using SMD components :)
and most importantly a cut off voltage

I have seen a good one from pololu here but i going to do a single board circuit. I have tried looking for what IC pololu is using but i could not find it (i also doubt that they will tell me). I also tried searching, but i am quite overwhelmed at the extra specs manufacturer give(frequency,Iq??,etc.) and dont know which one is for me

So i guess this question boils down to - can you recomend me a good buck boost converter ic that fits my need and has decent documentation that shows a sample circuit in order for me to create.

Edit: Based  on the chip and with the help of The Photon, i have made this circuit.


texts: Which Signals require impedance matching?

texts:
There are two types of connections in PCB.

Which are in between the PCB.(e.g- A SD card is connected near to Controller)
One is going out through some connectors.(Some UART or SPI going out through connector.)

My question is that both types of signals require impedance matching. Or just connection which are going outside PCB through wires require impedance matching.


texts: Measure the output voltage of photodiode in parallel with a laser diode

texts:
Since a photodiode and the laser diode is connected in parallel in a laser device, measuring the voltage across the photodiode can tell us how much power the laser is emitting.

The photodiode and laser diode is connected in parallel, the voltage produced in the photodiode should reduce the voltage across the laser diode, because the photodiode only allows current in one direction(?), I guess it is not just simply to measure the voltage as shown in the figure.

So, how can I get the output voltage of the photodiode?


texts:
I have got this strip of EL light. I am using it in a project where I am also using 2.4g and 5.8g band of RF. The DC inverter creates a lot of RF noise (understandably) as it's inverting from DC 12v. This is being used on an unmanned aerial vehicle, so weight considerations are part of the equation.

I am thinking of two solutions so far:

Faraday's cage - get some sort of conductive material and wrap the inverter in it.
Use a ferrite ring on the inverter inputs.

It's not clear to me that these solutions actually help with my problem. Are there any suggestions for other solutions?

Thank you!


texts:
I'm starting to learn how to program micro controllers.
This is my current setup.

When I'm trying to flash a Hello World program with AVRDude I'm getting the following message:

avrdude: initialization failed, rc=-1
     Double check connections and try again, or use -F to override
     this check.

I have checked most of the options in this guide but none of them seem to resolve this issue. Also using the 16MHz crystal does not help.

I wanted to ask you if you could check my setup and also point me to what I'm doing wrong.

Just to make it clear - my development environment is: Debian / Pocket AVR Programmer.


texts: What are the mechanism and effects of non-linearity in an attenuating barrier in the presence of a high-strength EM field?

texts:
It's my understanding that in electromagnetics, if an attenuating device is functioning linearly, it means that 1) input and output signal strengths are proportional; and 2) input f = output f. How accurate and complete is this definition?

It's also my understanding that an attenuating barrier can become non-linear in the presence of a high-strength EM field (e.g., 50 kV/m, 133 A/m). Why/how does this occur? What properties of the barrier material affect this (e.g., permitivity, permeability, ferromagnetic properties, etc.)?

It's also my understanding that non-linearity causes a barrier's attenuation to be enhanced or diminished by frequency, depending on the detail of the non-linearity. What is meant by "the detail of the non-linearity"?  Why/how does non-linearity cause attenuation to be enhanced or diminished at a frequency? In other words, what material properties determine whether attenuation increases or decreases?

Actually, if the definition of linearity in the first paragraph above is okay, then I think I understand, at least partially, why non-linearity might cause attenuation to increase or decrease at a frequency. If the non-linearity involves a frequency shift, then attenuation would increase at the input frequency and decrease at the output frequency. If the non-linearity involves a change in the proportionality of input and output signal strengths, then depending on how the proportion changes, attenuation would be increased or decreased. Do I have this right?

This is a rewrite of this question, which was titled and worded poorly. Selvek's answer was helpful, though. I would have asked him for clarification, but it didn't seem to make sense to contribute further to an unclear question that misses what I had intended to ask and that's inviting down votes. So, re-asking seemed a good solution. Apologies if this isn't correct procedure.  I'm new here. I did reach out for help from a moderator, but I haven't received a reply yet.


texts:
I'm trying to use an absolute shaft encoder with an NI MyDAQ. I'm powering the encoder using the 5VDC pin on the DAQ. Does the ground pin--AGND vs. DGND--I connect the shaft encoder to matter?

I started with the DGND since I was powering the encoder with DC, but my angle reading steadily "floated" down. For example, I would initially read a angle max of "-170" and an angle "min" of -130. However, the two extremes would then begin to float down to -171 and -131, -172 and -132, -173 and -133, and so on.

I switched over to AGND, but I experienced the same phenomenon. I realize my problem is independent of ground pins, but I'd like to know which GND pin is the correct pin for my application or if it truly doesn't matter.


texts:
I am attempting to connect a CMOS parallel SRAM chip to a few different 74HC chips, but mostly 74HC377 octal flip-flops.
I'm having inconsistent results with values being loaded sometimes not being correct. Looking at the data sheet, the 74HC377 has a high level input of 3.15V with Vcc at 4.5 volts, and the SRAM has a minimum high level output of 2.4V at the minimum Vcc, which is 4.5V. In my measurements, the SRAM high output is around 3.5 volts, and as Vcc is around 5.2 volts it's probably just barely enough to register as high to the 377, which explains the instability.
Why the heck is the SRAM high level output not just Vcc like everything else? I've looked for other SRAM chips that have compatible voltages but it seems like they all have this. What can be done to accommodate this? Or am I doing something wrong?
Edit: the SRAM chip is a Renesas 71256SA, and I measured the voltage using a multimeter.


texts: Danfoss BD2.5 on 12V starting problem. Good signal on only one gate of both driving MOSFETs

texts:
The winding resistances are OK, not shorted to ground. One of 3 compressor coils is 3.6 ohms (should be 3.5). Driver coil resistances is 0.2 ohm instead of the normal 0.3. Compressor turns 1/2 turn or less. I don't have a schematic.
I added some details on gate signals

Yellow is g1
Green is g2

Signal at µP is equal as at gate itself. MOSFET drains are connected to 2 coils with 0.2 (0.3) ohm resistance (BL and ZW marked connectors). A third coil has 3.5 ohm (marked WT). The 'Brn' connector (on the +) is common to all 3 coils. Is this motor BEMF controlled?


texts: What is "forward" and "reverse" voltage when working with diodes?

texts:
What is the difference between "forward" and "reverse" voltages when working with diodes and LEDs?

I realize this question is answered elsewhere on the interwebs such as wikipedia, but I am looking for a short summary that is less of a technical discussion and more a useful tip to someone using diodes in a hobby circuit.


texts:
I have some questions regarding PCBnew of kicad 5.1.0.

I cannot find how to global spread all the footprints after reading the netlist. There is no "mode button or footprint mode" any longer.
How can I change the size of several footprints' pads at the same time, avoiding the need to open each footprint one by one with the footprint editor and change its footprints?
I cannot find the button "update footprint into current board" any more in the footprint editor, so that my changes can be applied to my PCB.

In general, is there a way to manage the PCBnew toolbars?

Edit:

This is the top toolbar of this version's footprint editor. The "update footprint" button is missing:

This is the top toolbar of this versions PCBnew. The modes buttons are missing:


texts: What can I do to increase passive HF RFID read range?

texts:
I am working on a prototype, one function of which is to detect whether an object is "in range" by a few cm. Right now I'm just using an Arduino and a cheap Mifare RC-522 kit that operates at 13.56 MHz:

I've successfully gotten it to detect the tag, but only at a distance of about 3-4 cm when the tag is oriented parallel to the antenna.

According to my limited research, the HF band allows read ranges of between 10 cm and 1 m for passive tags, depending on factors like antenna size, tag size and orientation, and transceiver power.

I realize this inexpensive reader is not up to task as-is, but I'm interested in building something that achieves read ranges of 15-20 cm.

Some criteria:

No need to read multiple tags; only whether one tag is in range or not.
No need to write to the tag.
Cannot use an active tag.

I'm not experienced with RFID reader construction (yet) but am interested in knowing what I should pursue.

Here are some things I've considered:

Ditch the embedded antenna on the cheap RFID reader and construct my own, larger antenna. I'd need to see if the onboard MFRC522 is up to the task of providing additional power.
Look for a different IC around which to build a reader from scratch.
Find a ready-made solution instead of trying to build one (more cost-effective?).
Use something other than RFID for simple proximity detection.

I am experienced with microcontrollers and basic electronics, and have made audio and lighting projects, but this is a first with RFID. Since I don't need to read multiple tags, which RFID is suitable for, I've considered maybe some sort of magnet and hall-effect sensor, but the range does not seem adequate. I considered using an ultrasonic proximity detector, but the application calls for detecting the tagged object while ignoring untagged ones (ultrasonic would produce false positives on untagged objects). I've considered some sort of reflective surface placed on the object, and detecting reflected light, but the object orientation is not reliable enough to maintain alignment.

So, in a nutshell, What modifications can I make to my existing reader, or what alternate technology should I pursue to achieve 15-20 cm detection of a passively tagged object?

I plan on connecting whatever proximity detector is used to a microcontroller using SPI.


texts:
I trying to read RPM from my motorcycle's pickup coil by using Arduino, but the RPM is not that accurate.
For example, when engine idling, the RPM looks ok. When more throttle is opened, the RPM become inaccurate. I can feel the engine RPM actually quite low, maybe just around 3000 +-, but the serial monitor shown 5000 or 6000 RPM.
Here is the code that I copy from arduino forum and made some minor edits to the code:
int rpmpin = 2;
long rpm = 0;
unsigned long timerrevcalc = 0;
unsigned long duration;

void setup() {
  Serial.begin(9600);
  pinMode(rpmpin, INPUT);
}

void loop() {
  rpmCalculation();
  Serial.println(rpm);
}

void rpmCalculation() {
  duration = pulseIn(rpmpin, HIGH, 100000);
  timerrevcalc = duration * 100;
  rpm = 60000000 / timerrevcalc;
}

I have tried using two pulseIn (HIGH or LOW) method, or Interrupt. But I hope to stick with one pulseIn for now.
Can help to improve the calculation?


texts: how to get a fixed clock frequency from range of clock frequency input in verilog

texts:
I am writing a code in Verilog(FPGA) which works with the input clock frequency of 128khz, for my assignment my Ip core should be parameterized to work with clock frequencies from 128kHz to 100MHz. in order to do so, I should build a frequency divider circuit to create a clock enable signal for my servo controller. The frequency divider is used to reduce the incoming clock rate to a fixed value.
could anyone guide me on how to build the frequency divider pls?


texts:
I am still confuse about op amp.
When we need to use op amp? And how to determine the gain value for our op amp?

For example:
I want to use LM35 and atmega16. If the wire length between LM35 and atmega16 is short, i don't need to use op amp. If the wire length is too long, i need to use op amp, because there is possible of drop voltage.
But, how length the minimum wire that cause the circuit for need to use op amp? and what the exactly gain value for my op amp?


texts: Can a photodiode distinguish between daylight and white/blue LED?

texts:
I am working with a photodiode that is supposed to detect very tiny amount of LED light(the light will be programmed by an attiny 85). Using different kind of lenses I succeeded amplifying the light amount that will fall on the photodiode. Making use of op amps I could bring the photo detector to trigger an action (start a servo motor) as the small light amount was falling on it.

R1: 10M; Opamp: LM358; photodiode: VTB8440BH; Energy consumption should be as minimal as possible.

Now I have the problem as this experiment only works in dark environment. Since the photodiode has become very sensible with the op amp even small amount of daylight is detected by the photodiode.
The photodiode I make use of is  VTB8440BH (Datasheet Photodiode http://www.farnell.com/datasheets/57158.pdf.)
As per datasheet its sensitivity peaks at 500nm. Since the light source is a white/blue LED ( arrnd. 450nm) I have selected this photodiode.
However now I learned that even the wavelength of daylight settles btw 350 and 700 nm. Hence I experience the problem as mentioned above that the photodiode cannot differ between both the lights.
I am aware to avoid this issue I should/might use an Infrared Light source. I have also learned that I might use a filter to avoid daylight however in my case I doubt (not sure though) that only daylight can be disselected filtering the led light.
However I want to do it with an LED. Is there a possibility to avoid daylight and detect white/blue led???

I have already considered interesting discussions however I could not extract the required information for me to address my issue.
 how to make a system respond to IR laser?
Poor man's IR obstacle sensor make sense(improve) from signal under daylight


texts:
I'm implementing a system based on the STM32L0 line of microcontrollers that uses an external interrupt to trigger an SPI read from an external sensor (a DW1000 UWB module). I am not running any sort of OS. The microcontroller runs through all of the initialization code, but just before I enter the infinite while, I want to enable interrupts, so I call the __enable_irq() intrinsic found in CMSIS_gcc.h. When the microcontroller enters into the function, it does not return, and the debugger outputs the following repeatedly:

Performing single step...
...Target halted (DBGRQ, PC = 0x0800460C)
Reading all registers

The disassembly looks like this:
 __ASM volatile ("cpsie i" : : : "memory");
0800460a:   cpsie   i
0800460c:   b.n     0x800460c <main+144>
0800460e:   bl      0x80043f4 <Error_Handler>
08004612:   nop     ; (mov r8, r8)
08004614:   ldr     r0, [r0, r0]
08004616:   ands    r1, r0
08004618:   asrs    r0, r0, #32
0800461a:   ands    r2, r0
0800461c:   b.n     0x8004640 <RTC_IRQHandler+4>
0800461e:   b.n     0x8004622 <main+166>
08004620:   ldrb    r7, [r7, #31]
08004622:           ; <UNDEFINED> instruction: 0xffff0764
08004626:   movs    r0, #0

I'm thinking the line at address 0x800460c is suspicious because it shouldn't be attempting to branch to itself, but I am having a hard time understanding the programming manual and the .n suffix of the b instruction. The C-code follows:
  /* Ensures IRQs are only enabled once. */
  prim = __get_PRIMASK();
  if(!(prim & 0x01)){
      __enable_irq();
  }

...

__attribute__( ( always_inline ) ) __STATIC_INLINE void __enable_irq(void)
{
  __ASM volatile ("cpsie i" : : : "memory");
}

Any direction is helpful. Thank you!


texts: Voltage divider which will work for low and high frequency signals

texts:
I am using the below circuit (fig1) to step down the voltage, which I found on the internet.
I want this circuit to be operate properly from 1 kHz to 50 MHz. When the input is a square wave. But this circuit work properly in the range of MHz. But when the kHz frequency is given I am getting waveform like this (fig2).

How to calculate the value of R1 and C1?


texts:
I am looking into using an SPV1040 boost converter to charge a battery from a solar cell. The chip includes inputs for a current sense resistor, which are described in  one of ST's applications notes 1. Here is a screenshot of the relevant section:

It looks simple: Rs = 0.05 / Imax. But the reference design uses a 10mΩ current sense resistor, and this part's maximum current output is 1.8A. Wouldn't a 0.01Ω resistor mean a maximum current of 5A, following the above equation?

I'd like to limit a 350mAh battery to a 1C charge rate, but I'm not sure if I should trust the value of 0.05 / 0.35 = 0.143Ω that I get.

Also, if I'm planning to use a small solar cell which is unlikely to ever produce 350mA @ ~4.1V, can I replace this sense resistor with a 0Ω jumper? And if I did that, could I also drop the filtering resistors/capacitor without worrying about noise from the power supply?

Thank you all!


texts: I am trying to understand how a iv graph for a battery rated at 10V with internal resistance of 10 Ohms would look like. I was thinking it would just be a constant 10V for the graph, however, I am unsure how internal the internal resistance would impact the terminal voltage.


texts: I've read at several places (1,2) that ICs such a DAC have both analog and digital ground pins, both should be tied to AGND at the chip. However, the specific part I'm planning to use (MAX5104) does not claim so in the datasheet, showing instead that the DGND pin beconnecto to the boards digital ground plane. Why exactly is that?


texts:
Mostly the signals out of a audio source is represented by Voltage/Time graph; like this -

Then how would the Current/Time graph would look like, and what will happen if we alter it?


texts: I have a variable in my code where I can change "modes".  Some (timer and counter) values are reduced and I can run in Modelsim and enjoy the fast error checking. Currently, I need Signal Tap for real time testing as I am reading data from another source. The code needs to be compiled using QP. Also QP has some advantages as I can better understand the syntax error codes. Modelsim takes about a second to compile. QP can take at least a couple of minutes just to denote a syntax error. Is there a way to get "instant" syntax checking using QP by having it do some syntax checking first? I understand that there can be other errors besides syntax that can take a while to find. Total processing is 10 minutes and if it takes 6 minutes to find a fitting error, I am fine with that. However all of the errors I have corrected appear to be syntax related. I am using a windows system and I do not know anything about command line editing in QP.


texts: Does 20 Millegausse near outlet with nothing plugged in suggest faulty wiring?

texts: Meterk EMF meter showing 20+ millegausse near two outlets only. Both outlets have nothing plugged in. Possible live and neutral wires faulty?


texts: Changing iron's pilot lamp connection, will it still work?

texts:
I have restored a Rowenta E5291 heavy clothing iron, a remake of a vintage model, and I changed the pilot lamp's connection.

I made this change because this iron can never be turned off unless you unplug it so I modified the bimetal switch to allow it to be turned off when turning the button to the lowest setting. Everything worked good but it was still heating because the lamp was still directing the power to the heater so I have changed it in the following way:

Diagram of the wiring before and after the modification

But I am worried that it might blow up the lamp or trigger the breaker box. Since I strongly doubt I can find a replacement for the lamp, in case it gets busted, I would like to hear from anyone if this will work as I expect or if it will cause any problem.

Mind you that I am very amateur but I did check for continuity with a multimeter and everything looked good (Unplugged from the wall).


texts: Minimum burden resistor for current transformer

texts:
In calculating a burden resistor for a current transformer, what determines how low a value you can use?

Assuming you can still obtain the minimum voltage acceptable to the ADC, what other factors determine the lowest acceptable burden value?

I have a circuit where I have some margin at the minimum current end but I want to reduce the voltage at the maximum current end of the calculation. I can achieve this by lowering the burden value but I am not sure how low I should go.

This particular current transformer datasheet uses the minimalist approach and does not specify any burden values or DC resistance values.


texts: will For loop in MikroC for dspic block the interrupt service routine?

texts:
I am using MikroC for dspic30f4011. I am using a Timer3 interrupt for ADC reading. In this Interrupt services routine, I am reading ADC values. In Void main, where I need some delay in the instruction . will timer3 Interrupt will read the value of ADC and will update the ADC variable?  how will it work?

My question is that, if I am using an interrupt, will the delay in the Void main effects the interrupt. Will delay remaining while interrupting occurs?

one more, If use for loop for the delay as given below. If during for loop, interrupt occurs, interrupt will do its task and then start again from where it is interrupted

                               for(long q = 0; q<1000000; q++){
                                //
                                  }

if an interrupt occurs at q=100, after interrupt service, will the for loop start again from q=101?


texts:
I've been trying to find a good description of the TTL serial "standard" without much luck.  I understand that serial transmit (TX) and receive (RX) lines idle high (at VCC) and that they drop to ground when a bit is transmitted.  As such, they're inverted from the norm, where a "1" is high and "0" is low.

What I don't understand is who's responsible for holding the line high and how a zero is transmitted.  Does the sender drive the line to high and low? Or does the receiver hold the line high with the sender pulling the line low (open collector)?


texts: Altium: Plane assignment for split planes

texts: How can I assign multiple nets to a single plane layer? I've assigned the ground plane to net GND in the layer stack manager. But how can I assign nets 1.5V, 3.3V and 5V to the power plane?


texts: How to make a parallel connection between two components when each has its own voltage?

texts:
I have a problem to determine whether or not it is safe to make a connection as picture below. Currently I have a H7EC counter connected to a switch and it has 2.7 V  across terminal 1 & 2 on the counter itself (it should be a battery inside the counter). I was planning to branch out the connection parallel to PC COM port and there's 5.8 V across pin 2 & 3 of the PC COM port.
My question is: Is it safe if I make the connection directly as the picture? If not, what do I need to add in between so it won't do any damage to the counter/COM port?


texts: Why is a MOSFET triggered by Vgs and not Vgd?

texts:
Looking carefully at this diagram of one type of MOSFET:

(found in this application note)

We can see the device is virtually symmetrical. What makes the gate reference itself to the source and not the drain?

Also, why would the gate oxide break down at 20V Vgs and not 20V Vgd?

(Not a homework question. Just curiosity.)


texts: ATMEL 24C02 EEPROM - Trouble understanding how the addressing works

texts:
I am currently writing a library for ATMEL's 24C series EEPROMs (not a programming question). The library works fine with a single EEPROM at the moment and I am trying to support multiple EEPROMs now, since according to the data sheet, up to 8 24C02 EEPROMs can be connected at the same time. However, I am not able to understand how to assign an address to the EEPROM. From what I understand, I can assign an address between 0x50 and 0x57 by setting A0, A1 and A2 pins to HIGH or LOW. However, it doesn't matter what I set these pins to. The EEPROM uses all the 8 addresses:

I2C scanner. Scanning ...
Found address: 80 (0x50)
Found address: 81 (0x51)
Found address: 82 (0x52)
Found address: 83 (0x53)
Found address: 84 (0x54)
Found address: 85 (0x55)
Found address: 86 (0x56)
Found address: 87 (0x57)
Done.
Found 8 device(s).

This output is from I2C scanner. I can transmit with all of the addresses and the single EEPROM receives it all. Is there something else I need to do?

Here is the datasheet of the EEPROM: https://www.rhydolabz.com/documents/24c04.pdf


texts: Do you always need a separate ground for the power part and the signal part

texts:
In case of a Boost converter, one of the advantages that I always come across is the fact that you can use a simpler low-side driver. I fabricated such a Boost converter in open loop using the IRS44273I driver IC (Datasheet driver IC). The PWM is generated by a microcontroller that shares the GND plane with the driver IC (COM port in the drawing on the first page of the datasheet). I however heard that it is good practice to keep these two grounds separate (I don't exactly know why).

Is this also the case for a Boost converter? Would it be recommended to place some kind of digital signal isolator in between the µC and the MOSFET driver? For the moment I don't have any problems but I am making a new version of the board with measurements to drive it in closed loop. In case a separate ground plane is needed, I would like to add it.

I appreciate your help and comments on this topic.


texts: How can I record video with single camera module of smartphones?

texts: I want to record video apart from my smartphone(Let's say Samsung Galaxy S3) taking out it's camera module.I think it is possible because camera's microchip comes with itself.I mean I will connect camera to micro SD and I will give wanted DC current from battery and camera records and sends video to my micro SD card.If it is possible how can I do it?And how much voltage will be needed to record video continously?


texts: Typical vs Maximum External Flash Write Times

texts:
I have limited time to write to external flash in production and going by the typical page program time(0.85ms) is fine, but the maximum page program time(4ms) will not be fast enough.
The question is will all new flash chips be close to the typical time, and the reason for the maximum time is due to chips getting slower over time/cycles, or do all brand new chips vary between the typical and maximum times?
I asked the manufacturer for feedback and they didn't give a straight answer.
I am looking at the MX25R3235F part. See page 75 for page program times.
https://www.macronix.com/Lists/Datasheet/Attachments/7534/MX25R3235F,%20Wide%20Range,%2032Mb,%20v1.6.pdf


texts: Can I provided 3.3V regulated directly to the BBB

texts: I have a project where I need to be mobile and I draw a lot of power (4 BBB, 5 Port switch, 26 cameras). All of the cameras and the control circuits run at 3.3V - I'd love it if I could just deliver 3.3V at the main power connector and ignore the BBB 5V jack - is it possible to provide 3.3V to the BBB ? I swear I'll keep it well regulated (or pay the butchers bill if I don't)


texts: Voltage detector with ajustable time delay in a THT package or build own simple small time delay?

texts:
For my project I need to delay the enable signal from an esp32 for a 50MHz clock by a bit - The examples I use on how to do that only ever use a BD523 with non-inverted output. For testing I want to build this on a perfboard because the guide I followed (and experience I made) don't allow me to use a breadboard as the 50MHz signal doesn't work with it.
I tried to search for a part on RS but I simply couldn't find one that was ideal for my purpose.
Does someone have an idea on how I could implement that on my own ?
As for why:
The ESP32 signal goes into PIN0(can't change because it's the EMAC CLK Pin) which is also a strapping pin to enable to programming if pulled LOW. I already put a 10K pull-up on the pin. The clock get's powered by the 3V3 out from the ESP32 so in a 50/50 chance the PIN0 is either HIGH or LOW on startup depending on the clock which I don't want. I need to delay the 3V3 clock enable for a few (milli)seconds so it doesn't load into the boot mode.
Example on how it is made with a BD523 (here with PoE wich I don't need/have) WESP32


texts: Can a 12-24Vdc, 2A, 4 Channel light controller for strip lights be used to control (5) CREE 3.1V RGBW LED Emitters in Series?

texts: Will a 12-24 Vdc, 2 Amp Max, 5-Pin Strip Light Controller, with IR Remote, the ones commonly available for multicolored strip lights via Ebay, work to control (5) CREE XM-L RGBW 10 Watt LED Emitters connected in Series? If not, please advise why not.  And, if there is another way to wire up the CREE LEDs and still use the strip light controller, perhaps in parrallel, then please advise how to do that.  I like the small footprint of the strip light controller, which has terminals for all of the colors available, and provides 12-24 Vdc.  But, I have heard that strip lights are wired in series sections and joined in parallel at each segment of 3-6 leds in order to form the complete 300 led strip. I don't want to blow the CREE LED Emitters if I wire them up in series, and apply the strip light controller to the circuit...but, it would be nice if I could make it work somehow due to the small footprint of the strip light controller, versus having to install Meanwell brand controllers for each of the respective colors.


texts: Can anyone give an explanation about general impedance converter? This question might not be specific enough, but I will appreciate if someone could share as much as possible about this circuit.


texts:
I don't use the word "modulated" very much and I would like to make sure I use it correctly.  The TSSP77038 IR receiver module is a device that detects infrared light turning on and off quickly at a frequency of 38 kHz.  When it detects light like that, the output goes low and stays low until the signal disappears.

Is it appropriate to describe the TSSP77038 as a "38 kHz modulated IR sensor", since the infrared light wave needs to be turned on and off at 38 kHz?  Or would the word "modulated" only apply to the gaps that one would insert into a 38 kHz IR signal in order to transmit actual data?

Opinions are welcome, but the best answers will cite trusted sources or make a compelling argument.

Additional info

The TSSP77038 datasheet does not use the word modulated.

Wikipedia describes modulation this way:

  In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.


texts: drive 3 phase induction motor with only DC (not pwm) thru each phase

texts:
I've been researching making a driver for a 3 phase induction motor powered by DC source using PWM to approximate sine waves in each phase.

However, the switching speeds of the PWM signal for the rotational speed I want is difficult to obtain with hobby microcontroller boards like the arduino.

Can I just switch the DC directly thru each phase at the correct time only twice per cycle ?  Essentially I would be approximating a sine wave with only 2 different voltages thru the coils, ie: +V and -V (using H bridge circuitry here)

Will this create enough of a rotating magnetic field that sufficient current is induced in the rotor cage ?

What will be the losses in power / efficiency for this, or any other drawbacks for this system ?

The bonus is greatly simplified drive electronics.


texts: Is using a display panel as a light sensor conceivable?

texts:
Though the question may sound naïve at first, I still wonder if it would somehow be possible to use an LCD/TFT/OLED or other Panel as an image-sensor.

From my understanding of how these kinds of displays work I’d imagine it would at least need a totally different type of controller to read out possible light exposures of the display pixels.

I guess a TFT would not work, but are there other types that could work, even monochrome?

I’d appreciate if someone who is into this kind of technology would like to elaborate on this.


texts: Is a higher capacitance rating ok for filtering?

texts:
I am newer to electronic design and bought the mpu6050 sensor chip, which the documentation can be found here:
https://datasheet.lcsc.com/szlcsc/TDK-InvenSense-MPU-6050_C24112.pdf

It says that pin 20 connects to 2.2nf cap to ground, however, I don't have one that small. The smallest I currently have is 100nf. I believe that the cap is used for power filtering.

Is ok to use that large of a value in replacement, can I hook up a few in series, or do I need to go and buy the 2.2nf rated ones?


texts: Wiring problem while making couple of USB Type-C cables

texts:
1. USB TYPE-C to USB 2.0 Standard-A Cable

Found this TYPE-C connector parts w/ 56k resistor from taobao, but there is no detailed circuit diagram on it.

I want to make USB TYPE-C(device) to USB 2.0 Standard-A(host) Cable with this.

USB type-c specification document says,

  Pin A5 (CC) of the USB Type-C plug shall be connected to VBUS through a resistor Rp (56 kΩ ± 5%).

Question A : Can I assume that the 56k resistor is used for PULL-UP resistor as the spec requires?

And the connector has two copper pads for each of VBUS, GND respectively.

Question B : Should I connect both side of copper pads for VBUS and GND? or Can I ignore the opposite side for each of them?

Question C : Should I avoid 10NF capacitor for this type of cable?

2. USB Type-C to USB 3.1 Standard-B Cable

Also found this TYPE-C connector parts w/ 5.1k resistor and 10nf capacitor,
and sure enough, there is no detailed circuit diagram on it.

I want to make USB Type-C(host) to USB 3.1 Standard-B(device) Cable with this.

USB type-c specification document says,

  Pin A5 (CC) of the USB Type-C plug shall be connected to GND through a resistor Rd (5.1 kΩ ± 20%).

  All VBUS pins shall be connected together within the USB Type-C plug. A bypass capacitor is
  required between the VBUS and ground pins in the USB Type-C plug side of the cable. The bypass
  capacitor shall be 10nF ± 20% in cables which incorporate a USB Standard-B plug. The bypass
  capacitor shall be placed as close as possible to the power supply pad.

Question D : Can I assume that the 5.1k resistor is used for PULL-DOWN resistor as the spec requires?

Question E : Can I assume that the 10nf capacitor is used for bypass capacitor as the spec requires?

Question F : Can I ignore copper pad for CC? (leave opened)

I'm especially worried about the second one, cause someone said this can fry my laptop up if I choose the wrong parts.

Anyway, thank you for reading this.


texts:
I am making a real simple 8x8 led array (each in parallel).

According to this, can I just skip the resistor?
Also, I have a usb charging port capable of 2.1A 5v. Can I just use the generic usb cable to  bus the power? Is there any problem that you can see? (last thing I want is burning out some thing)


texts: Termination of SY cable shield at VFD and 3 phase motor?

texts:
I am wiring a single to 3 phase VFD to a 3 phase motor (240V delta). The 3/4HP motor powers a lathe in a domestic setting. Supply voltage is 240V 50Hz.

As per the VFD instructions, I am using shielded cable (SY 3 core plus PE) between the VFD and motor and have used the motor cable shield clamp at the VFD. Additionally, I plan to connect the earth wire at the VFD and motor.

VFD datasheet: http://www.elektro-trading.com.pl/pdf/napedyac/601/HA464518.pdf

My question is should the SY cable shield also be terminated at the motor? Safety is my priority and I would also wish to minimise electrical noise.


texts: How does a 32-bit DSP address 2³² values without enough RAM?

texts: A 32-bit CPU in a PC is capable of addressing 2³² individual bytes. How do DSPs and microprocessors handle such a large address space when they have RAMs only in MBs at the most?


texts: Capacitive current leads, inductive lags, but how does this translate to voltage on an output?

texts:
I'm really confused about the capacitive current leads the voltage, inductive current lags the voltage. The reason for this confusion is the graphs I've seen in different sources trying to explain this, the inconsistancy has really made me question everything I know about voltage and current.

One source used $$ V_R ; V_L ; V_C $$ to show that Vc leads i, VL lags i and VR will be in phase. Another source used V_S and showed the currents respectively leading/lagging the input voltage.

This probably sounds stupid, but it has confused me a lot now, is the voltage across the capacitor in phase with the voltage source, but the current through it is out of phase? Or is it something else?

In my scope readin, I have an RL circuit with the output voltage leading the input voltage, but in an RLC series circuit (below resonance when -X_C > X_L right?) I have a similar output with the output voltage leading the input.

When people say I_c leads V, is the V the voltage across the capacitor or the voltage source?

Edit

Firstly I really apprieciate the answers, all have been a lot of help and its helped me to understand the concept a lot more. I have still some doubts, particularly when it is applied to a real example. I made up an LCR circuit in series. I checked out the maths for frequencies at 4100Hz and 5500Hz (resonance was about 4.81kHz. At 4100Hz, the angle of impedance is \$-82^{\circ}\$, this is what I expected since the \$-X_C > X_L\$ giving \$\theta = \arctan(\frac{X_L - X_C}{R})\$ so \$\theta\$ is negative.I got the info from this site, the current/voltage plots are towards the bottom of the page

Similarly for 5500Hz, \$-X_C < X_L\$ and results in a postive angle of impedance ( \$75^{\circ}\$) as expected.

What I do not understand is how I have a negative angle of impedance, but the phase shift is positive and above resonance, a positive angle but negative impedance. Am I misunderstanding or should I indeed have a lag where it is leading and a lead where I have a lag in the readings below?

Or should I be taking this a step further and calculating the voltages across the components, as shown in the first example here? using this method, I get a positive angle of \$86^{\circ}\$, however I the capacitor voltage is greater than V across the inductor, which would surely result in a negative phase angle? Likewise, at 5530Hz, I calculate (using the same method) a phase angle of \$76^{\circ}\$, which \$V_L > V_C\$, which surely means a positive phase shift?


texts:
How to implement subtractor of two 4-bit numbers using subtractors of two 1-bit numbers as a module(no assembler coding, just expressions in boolean algebra)?
If there are four 1-bit subtractors, how to find expressions for outputs of each?

For example, 3-bit comparator implementation using 1-bit comparators gives:

for A2A1A0 > B2B1B0
X=(A2>B2)+(A2=B2)(A1>B1)+(A2=B2)(A1=B1)(A0>B0)=X0+Y2X1+Y2Y1X0

for A2A1A0 = B2B1B0
Y=(A2=B2)(A1=B1)(A0=B0)=Y2Y1Y0

for A2A1A0 < B2B1B0
Z=(A2<B2)+(A2=B2)(A1=B1)(A0<B0)=Z2+Y2Z1+Y2Y1Z0

Truth table for full subtractor:

A B Ci R Co
0 0 0  0 0
0 0 1  1 1
0 1 0  1 1
0 1 1  0 1
1 0 0  1 0
1 0 1  0 0
1 1 0  0 0
1 1 1  1 1


texts: I sometimes end up having someone's unwanted old electronics, usually faulty ones. Does it make sense to harvest components from such. Anything valuable I should be looking for?


texts: Wireless doorbell transmitters and receivers

texts:
Im a complete noob when it comes to electronics but have been searching google and havent found anything and was just wondering if any of you can help guide me a little.
So I have this set of wireless doorbell and receivers, and Ive found mixed things on the internet as to whether or not Im able to pair more buttons to the existing set of receivers, and if there is a limit on how many I can pair.
Does anyone know if I can find this out from looking at the circuit boards, and if im only able to have the button is it possible to change it to be able to pair more than this. Really would love some guidance on where to begin and any help would be really appreciated :)
In the end id like to have a set of 6/7 buttons and 2 receivers, but can't find a set like this online which is why ive turned to stack exchange.
https://www.amazon.co.uk/Wireless-Doorbell-AVANTEK-Waterpoof-Operating/dp/B07KG9VXF6/


texts: Two diodes in input stage of power amplifier

texts: Some of the power amplifier schematics include diodes in input stage like below. What is the purpose of them?


texts:
What will be the Fourier transform of ramp function? Actually I got some results regarding this on the internet, but I was wondering how it could be possible because Fourier Transform (as I have read) is defined only for those functions which are converging or in other words which follow Dirichlet conditions.

There is one more question: Fourier transform is defined for signals with finite energy (converging functions), or in other words energy signals (which means finite energy and zero power) but when it comes to power signals (which means infinite energy and finite power), how power signals can also have their Fourier transform though they have infinite energy (e.g sinusoidal signals, unit step, DC signal etc.)?


texts:
How can I filter a DC offset of a pulse train with an RC circuit?
The signal is a pulse jumping between 3.07V and 3.53V. But I need a pulse which is jumping between 0V to 0.5V. How can I filter that 3V DC offset?


texts: How to connect arduino with shield correctly?

texts:
What is the good and not permanent way to attach arduino with shield?

I try to attach it with sparkfun usb shield via pin , but sometime it did not read unless i apply some pressure on it, then it will read and the usb host shield light will on.

USB host shield
http://www.sparkfun.com/products/9947

Arduino Uno


texts: Connecting two PSUs in series and parallel

texts:
So I have 2 identical 1W DC-DC converters (9V -> +/-5V). The converters are isolated to 6kV. The exact part is: XP IHA0109D05.
If I connect both (using the same battery for each one) in parallel will I get the same voltage at 2W (0.2A at max pd)?
And, in series, -10v -5v 0v 5v 10v at 1W (0.05A at max pd)?
Thanks.


texts: Need help understanding PNP Base into NPN Collecter circuit for LED Array

texts:
I am a novice in circuitry and I'm trying to make an 8x8x8 LED Cube using an instructables guide for a school project. I have ordered all the parts and was testing the grounding circuit for each layer (pictured below). I am trying to understand how the PNP and NPN transistors interact. The PNP is a TIP42C and the NPN is a 2N2222.

The PNP's (O1-O7) Emitter is connected to 5V, the Collector is connected to the cathode end of 64 LEDs, and the Base is connected to 5V through a 10Ω resistor and to the collector of the 2N2222 through a 1kΩ resistor.

The NPN's (T1-T8) base is connected to a MUX through a 1kΩ resistor, the emitter goes to ground, and the collector is from the PNP. I understand how this portion works.

R1-R8 and R17-R24 are 1kΩ. R25-R32 are 10kΩ.

What I don't understand is why the PNP transistor is necessary. I tried to build one line of the diagram:

Green Wire: High/Low to NPN Base
Black Wire: Ground from NPN Emitter
Orange Wire: Cathode from 64 LED Array (simulated with 3 LEDs)
Red Wire: 5V to PNP Emitter
White Wire: 5V to LEDs

But the issue I ran into was with the 5V into the Emitter of the PNP (Red wire). If I took that out, the LED's lit up, but the diagram clearly has the emitter of the PNP wired to 5V.

Is there some fundamental property of PNP transistors that I am missing? I calculated the total current of the 64 LEDs (~1.2A). (Is this right?) and would this circuit support that?

FYI, each line from JP2 in the first picture is a ground line from a 64 LED array and the lines from the IC1 are driven by an arduino uno.

I've been racking my brain over this for the last week and can't figure it out so any help would be greatly appreciated! Thank you!


texts: In search for the part on the picture (freehand circled in yellow)

texts:
I'm on the hunt for the yellow circled component. I ripped it off after opening the toothbrush
and changing the bad on/off button. Sadly i have few clues what it does:It is connected with the charging process of the brush. When on the charger it signal that it is loading (flashing light) but in reality the battery does not charge.
I tried to find it on http://www.s-manuals.com/smd
and with https://www.sphere.bc.ca/download/smd-codebook.pdf
but could not narrow it down in the slightest.


texts: How Would I Nomalize Cable TV Volume Between Commercials and Programming

texts:
I have had it with commercials on cable TV being a lot louder than the program I happen to be watching. I have also had the reverse where the program switches scenes and you cannot make out what the whispering actress is saying.

I know products are already on the market that take care of this problem, but I thought it would be fun to fix it myself. I come from the microprocessor/digital side of things so I really have not played with audio a whole lot.

I current use RCA audio cables between my cable box and sound system. I would like to plug my device between those two devices so that my amplifier receives the modified normalized audio signal.

So far I have been looking at Automatic Gain Control circuits as a solution. Is this the right way to go or should I be looking at something else?

If possible, please include links to schematics, components, etc with your post. Thank you in advance for your help.


texts:
I am making an Eagle part for the WDC 65C02 part (QFP version).

I can't find any specific package info in the datasheet other than the pinout, and the fact that it's a 44 pin QFC.

My question is, "Are all 44 pin QFC packages the same, and if so, where do I find the specific info I need to make the Eagle footprint?"

Thanks!


texts: Could I use a 2Ch 6bit LVDS cable on an LCD that uses 1Ch 6 bit LVDS?

texts:
this is my first question here so I'll try to make it as clear as possible.

I've bought a T.V53.03 control board to use with an old laptop display I have at my home. After searching for the display model I found it to be an LTN133AT09 display, which uses a 1Ch 6bit LVDS cable. The problem I have is that the control board ships with a 2Ch 6 bit LVDS cable, and I was wondering if it will work out of the box with the display.

In summary, my two questions are:

¿Will the LVDS cable work out of the box with my LCD?
¿Can i cut out some wires of the LVDS 2Ch cable to make it compatible? Or should I buy a 1Ch cable?

Thanks in advance for the answers!


texts: Why is this the voltage gain formula in the two-stage feedback amplifier?

texts:
In Albert Malvino's "Electronic Principles", he said that in a well-designed two-stage feedback amplifier for small signal operation(picture below) , the voltage gain equals $$A_v=\frac{r_f} {r_e}+1$$

Why does the voltage gain equals to this? I read before that the overall voltage gain of a two stage amplifier(without the feedback) is equals to the product of the voltage gain of the each stage. But when feedback resistor is added, it now only depends on this feedback resistor.


texts:
This unusual plug interfaces an electric hair dryer to the 120V 60Hz mains. The thing that makes it peculiar is that when it is tipped back and forth, a small 'clunk' can be felt, as something inside shifts in response to being tilted.

It is a small boxy thing, about a 1.75" x 1.25" x 1", has no ground lug, but is polarized. The wire coming out of it almost certainly carries 120VAC. There is a molded-in warning not to replace, open or immerse the plug. There are no openings of any kind, nor any obvious ways to disassemble it non-destructively.

What would clunk back and forth inside there?  It probably isn't an isolation transformer, not in a box that size, for 1800W. I doubt it's a tilt sensor, but can't rule that out. A replacement fuse might be about the right mass, but wouldn't be much use in an box that can't be opened. Anyone know what this is, before Mr. Plug is introduced to Mr. Hacksaw?

Mr. Plug's mugshot ..

No buttons of any kind. That metallic looking spot where a screw might ordinarily be is absolutely flat, and doesn't move. There are two not-screws like that, the other one is not visible in the picture, being hidden behind the right-hand prong.

follow up ..

After removal of the cover, a circuit was revealed:

Turns out that the the thing that went clunk was that inductor in the foreground. Interestingly the connection on the right side failed, so the loose inductor was just wagging up and down. You can just see the hole in the wiring board where the lead was meant to connect.


texts:
Before I formally crimp:I am using 22 AWG wire and the crimp fits 22-26 AWG. I tried very hard to shove the wires inside the head of the crimp, to no avail. The picture below shows how my wires stop at the "crimped area" of the crimp.

My question is: is it necessary to shove the wire all the way in when crimping? Thank you!


texts: How are and what are the sources coupled to a 3-wire RTD leads?

texts:
I can understand two or four wire connection for RTDs. But I don't get where they apply voltage or current and how they measure the resistor values for 3-wire connection:

Here is a page about these lead compensation techniques. In the 3 wire technique how are the resistors measured? In other words I want to see the current or voltage source connected to the three leads. Can someone illustrate how the source attached?

I'm asking how the current and voltage source are connected. The suggested duplicate doesn't show sort of thing explicitly. In short I dont get my answer when I read it. There is no current source there unlike in RTD.

Edit:

One of the answer suggested a circuit. I also found a similar one here.

But what Im stuck at is why is R3 necessary instead of a short? When I vary its value in simulation neither VM2 nor VM1 change at all. What is the function of R3 here? R3 is floating doesnt pass any current


texts:
I am a relatively newbie here and I am trying to build this project... so do not kick me hard and forget any stupid errors you see on the project. I appreciate any suggestions, criticism, etc., preferably with instructions on what to do. Talk to me like I am 3 years old. Show pictures...

Open this image on another window, or you will not see it with enough zoom.

This is a 4 stereo input switch. You press the key and you select the input key you want to send to the output.

First look at my power supply. I am using LM7810 and I have a resistor divider. So, My power supply is delivering +5V, 0 and -5V.

By having "negative voltage", I can setup the audio on the middle of the range and supply the MAX359 with positive and negative voltages.

I turn the whole thing on and it works almost perfectly. Every press of the switch and the next input is selected.

Now look at pins 8 and 9 of MAX359E (the switch). These lines enter on the potentiometers. The midle of the potentiometers go to the amplifier (TEA2025) and the other side of the potentiometer goes to -5V.

I have two problems with this circuit:

Noise. It is humming like hell on the output.
Another thing is that I am not sure if some voltages are correct. Suppose I put the multimeter's positive probe after C16 and the negative probe at -5V. If input U4 is not the selected input, that voltage is 5V as expected. As soon as I select U4, the voltage drops to 2.42V. I was not expecting that to drop.

Any ideas? Please remember to talk to me like I am 3 years old. Thanks.


texts: I am unable to determine the function of this circuit. The second stage looks like an integrator, but the presence of a pot in stage 1 really confuses me...


texts:
I am having an issue with DC gain for a non-inverting op amp circuit. All I am trying to do is double the voltage from two DAC outputs (DAC range is 0 to 5V and I want it to be ~0V to 10V). The DAC output is DC (<10Hz). The op amp I am using is the TI TL974 datasheet link: http://www.ti.com/lit/ds/symlink/tl974.pdf. I am using two 1kohm resistors in my FB loop to set my gain of x2. When I input 1V and 2.5V into the op amp I get the correct values out, 2V and 5V. But when I input 5V I only get ~7.5V out. This is a rail to rail op amp and the supply voltage is 10.5V so I would expect that I should get 10V out or really close to 10V.

The output source current spec for the op amp is ~1.2mA so I thought maybe my feedback resistors are too low a value so I tried 10kohm resistors and the problem got worse, went from 7.5V out to 7V out. My load is a benchtop DMM. I attached a 10kohm resistor as the load and measured the voltage across it and things got worse again. The output voltage dropped to ~6.7V. When I just connect the DMM as the load and I set its input Z to max the voltage goes up a bit. Seems like a loading problem but if that were the case then raising the value of the feedback resistors should have helped and not made things worse.

Any help would be greatly appreciated,

(More traditional schematic representation shown for clarity)

simulate this circuit – Schematic created using CircuitLab


texts: Full bridge rectifier - in depth explanation

texts:
Most explanations of full wave bridge rectifiers start off with a diagram like the one below, and
then go on about what will happen on the positive and negative cycle of the AC input voltage. This is all fine and well, but I would like to understand what goes on at a deeper level.

During the positive cycle, diodes D2 and D3 will conduct, but let's stop right here: the depletion region of D2 will only be forward-biased (start to conduct) if its anode is more positive than its cathode. But for this to work, terminal 'a' would have to be at a lower voltage than D2's anode initially.
I don't see any defined potential for terminal 'a' in the beginning, but with 'a' floating, how can the bridge begin to rectify?

Clearly, some of my assumptions must be faulty, but I don't see it.


texts:
I am designing a power circuit based off an older circuit for a similar machine, and have had a few issues in LTSpice simulator, where massive currents are drawn for the capacitors charging.

The image above shows the capacitors spike at the frequency of the AC input, quickly charging, but drawing a huge amount of current per cycle.

The instantaneous current draw (approx 120Hz) is 18A, and I am wondering whether this value is harmful to the operation of the circuit (currently under a 3.15A fuse), as the normal DC load is under the fuse normally.

Circuit voltage vs total current draw

Circuit outline (Simplified)

(I've got ways to manage inrush current, but not the constant spikes)


texts: Why are resistor values constant in the face of changing voltage and current?

texts:
Small question, I see that resistors are labeled in certain increments (e.g 5, 10 50 Ohms), although a resistor outside of a circuit is completely without voltage and therefore current. Does this just mean the resistor has a certain value when placed in an average circuit?

Also, I thought that, according to Ohm's Law, resistance was a variable along with current and voltage. Is this not true? I mean, if I speed up electrons through an ioninc matrix, through an increased voltage and current, shouldn't the matrix push back harder as well making more resistance?

I'm thinking of an ice cube falling through molasses. If the ice cube speeds up (due to increased push i.e voltage) shouldn't the molasses push back more as well? And yet it seems that resistors have a constant value, what the heck.


texts: Tool for "designing" a resistor network?

texts:
I'm preparing to calibrate some current sensors for a system with DC 13.6V power, and various loads, from well under an amp, up to about 4 amps. I bought some 2, 3 and 5 ohm power resistors, and plan to arrange them in various series and parallel networks to calibrate each current sensor using a load with known resistance.

It's easy to calculate the resistance of some resistors in series or in parallel, but I don't have a technique for generating a network with a desired resistance. I would like to come up with values that result in "well rounded" maximum amp values, such as very nearly 5 amps for the circuit that is supposed to max out around 4 amps, but so far I've just been making guesses. Sigh.

Is there a tool for doing this, or a reasonable "by hand" method? Thanks.


texts:
This question has been asked multiple times but I don't see anyone quoting hard evidence.

This link states that all devices that oscillate above 9 kHz need to undergo certification. (I would leave a comment on this question but my low reputation forbids me to do so)
This link (see ka7ehk's post) states that only compliance is required but certification is not necessary

However, neither link quotes from 47 CFR 15. So, my question is if FCC certification is required in the unlicensed bands in the USA? If so, where is the exact section in the 47 CFR 15 that states this bit of information?

PS: I'm going to start looking deeper in 47 CFR 15 but if anyone is super familiar with the spec, that would save me (and many other engineers in the future) a ton of time.


texts: Do 4 batteries capable of outputting 0.5 A in parallel give the batteries a max output of 2 A?

texts:
Sorry for the long question, but I couldn't think of another way to word it.

I'm working on a bicycle modification that requires 12 Volts, 4 Amps of power to run. I don't really want to buy a $80 car battery, and a low battery life is fine for this modification, so I was thinking of using a lot of AA batteries instead. From my calculations, it would take a minimum of 24 AA batteries to give that amount of power for one hour. But the problem is that my calculations assume that the capacity not only doubles, but so does the max output of the battery of batteries, something which I am not sure is true.


texts: Help understanding current direction with transistor?

texts:
I'm an electronics hobbyist struggling with the concept of transistors. I made a simple circuit with a PNP transistor based off of a diagram, but don't understand how it works.

From the book containing the diagram:

  Look carefully at schematic I. You see there are two paths for the current: one from base to emitter and another from the collector to emitter. The transistor is a PNP type. Notice the base to emitter path is open until you press the key.

What I dont get is the direction of current flow. I read that current has to flow against the direction of the arrow, but looking at the circuit, how could the LED light up if electrons can only pass the other direction? (opposite the blue arrow?)

Also I would really appreciate an explanation of the values for power sources (3V and 6V); On the board, V6 is 9 Volts while v4 is 6 volts so I'm unclear how they arrived at those values. Really appreciate your help; I've spent hours researching this and still am baffled.

Here's a picture of my circuit board:


texts: Using Quickfield LabelMover to extract specific local values at coordinates

texts:
Quickfield Student Edition
I've attempted using Quickfield's LabelMover Serial Analysis to automatically get local values of interest at a set of different specific coordinates, but I couldn't find a way to extract values from specific coordinates.
The help section doesn't specify my problem, I did however find that viewing the "Contour" shows me multiple points.
I'm not sure if this is the right Stack to ask about app usage, I feel like it's relevant.


texts:
I have a brushed motor and an ESC for brushed motors
 Motor rating is 12V 3A. ESC is the mod in the title. I have tried so much, but couldn't find a clue to find a relation between the led blinking, and how to speed up, change direction of the motor with the esc. I searched internet and also on the data sheet but couldnt finx a way out. Please help me?  I have access to a function generator, if that helps. Thank you.


texts: How to maintain a stable voltage on a Wind Turbine for Inverter

texts:
I'm doing some experiments on a wind turbine in my spare time.
At the moment, my system runs well and I can measure good output values from my generator. For example:

38V @18Hz at 30 RPM
97V @37Hz at 60 RPM
220V @72Hz at 120 RPM
343V @108Hz at 180 RPM
466V @144Hz at 240 RPM

The maximum measured current output is 18A.

Now, I would like to use an inverter in order to obtain a three phase output.
The problem is that I tried to search on the net and I only found inverters for solar panels which require a stable voltage input (my rectified voltage output keeps changing depending on the RPMs).
My system has a variable voltage output depending on the RPMs (obviously) and the frequency changes when the RPMs increase, too.

What is the most suitable solution to obtain a stable voltage output regardless the input RPMs?
Is there a commercial inverter which accepts variable inputs?

Thank you!


texts: MOVs, thermal fuse and thermal runaway behavior

texts:
Above picture is that of a Belden surge protector with some kind of cloth covered over the MOV and thermal fuse for isolation to promote more conduction.  I don't want to cover the whole thing with compound but something akin to cloth or other cover.. do you know what kind of cloth can't burn? or what more solid cover I can put that won't conduct and short the other elements? What do others use?

I'm designing a circuit and want to embed MOVs (Metal Oxide Varistors). I'd like to know two things:

I'm thinking of adding a thermal fuse. I read that the basic purpose of them is for temporary overvoltage (TOV) event when they can open before the MOV gets so hot and at end of life stage (where the MCOV kept decreasing gradually from each surge until it conducts at normal voltage initiating thermal runaway). But how about in actual surges.. if the MOV is rated at 3kA and you have a surge that is, say, 50kA, would it make the MOV initiate thermal runaway or not? How big should surges be compared to the MOV surge current rating before thermal runaway (bursting into flame) can occur?
Normal design is to put the thermal fuse beside the MOV. But does it depend on ambient temperature? If the room is cold with aircon.. can it prevent the thermal fuse from working?


texts:
I have been struggling some time trying to read data from my EEPROM 25A512.
I'm using a STM32F407IGT to access the EEPROM via SPI, but no luck reading or writing.

The SPI is configured using CUBE MX and HAL.

When I try to read the status register I send the following data:
Logic analyzer capture

In the picture below the timing sequence of the 'read status register' instruction is shown:
Read status timing sequence

Here is a schematic of my physical connections.

Here is the code I use for transmitting.

uint8_t len = 2;
uint8_t txBuf = EEPROM_RDSR;
HAL_GPIO_WritePin(SCS1_GPIO_Port, SCS1_Pin, GPIO_PIN_RESET);
HAL_SPI_Transmit(&hspi2, & txBuf, len, 100);
HAL_GPIO_WritePin(SCS1_GPIO_Port, SCS1_Pin, GPIO_PIN_SET);

Defines:

#define EEPROM_WRITE     0b00000010
#define EEPROM_READ      0b00000011
#define EEPROM_WRDI      0b00000100
#define EEPROM_RDSR      0b00000101
#define EEPROM_WREN      0b00000110
#define EEPROM_RDID      0b10101011
#define EEPROM_CE        0b11000111

Is there someting im not paying attention to? Why does the EEPROM not respond to the read instruction?

EDIT:
- Added new capture


texts: How do I safely measure secondary transformer voltages (Or ratio to primary)?

texts:
Let me begin by saying that I am a hobbyist, and I've been stupid with transformers before and I'm fed up with that.  This question doesn't have to do with design so much as just not killing myself, so I hope this is the right place.
I have a step-down transformer with no external wiring to allow it to easily interface with mains or a load.  The transformer is salvaged from nonfunctional equipment, I have confirmed continuity between each secondary tap and continuity between primary taps, and discontinuity between the primary and secondary. I don't know anything about the ratio between primary and secondary windings.
Is there a non-hacky (but preferably time-saving) way to measure the secondary voltages?


texts:
I connected three piezoelectric sensors to a rectifier which was further connected to a capacitor (100µF). I kept hitting the sensors for some time, and measured the voltage across the capacitor using a multi-meter. It displayed the voltage to be around 6 volts. Then, I used a breadboard to connect the capacitor, a resistor (100Ω ± 5%) and an LED bulb. The bulb didn't light up even for a fraction of a second. I measured the voltage across the capacitor again and found out that it had been discharged.
Any suggestions on how I can fix this?


texts: Which side is the shield's drain cable connected and why?

texts:
I have 2 PCBAs connected using a shielded cable. The cable is transmitting an SPI signal from master PCBA to the slave at 30MHz. I have previously been advised to shield on the driving circuit (master.)
Could some one explain the reasoning for this?
I have sensitive circuitry on the master board, why would I want to couple any noise picked up on the shield back to my master ground?


texts: When can free-floating electrical contacts become dangerous (e.g., start a fire)?

texts:
In general, when should free-floating electrical contacts be considered potentially dangerous?  Danger may be direct (e.g., due to electrical shock) or indirect (e.g., due to fire risk).
In this question on SE.SuperUser, a poster asks if it's safe to have two wires for a power switch exposed in their household.  Their concern seemed to focus on electrical shock to a person or pet.
The dangers of electrical shock to humans is discussed in these questions:

"How much voltage is “dangerous”?"

"Safe current limit for human contact?"

This YouTube video claims that 12V can start a fire:

Can 12 volts start a fire? Yes! Wake up people. Every day I hear people say "oh it's only 12v it can't do much". Shock wise, you're safe. Fire wise, treat it like line voltage, do it right, and safely. Because this can happen in your car, or even a charger. Electricity is electricity. It causes heat, and under the right condition, a fire...
Keep this in mind with your car audio installation too! Do it right, and make sure it's fuse protected!!
-"Can 12 volts start a fire?", YouTube

Presumably, we can construct hypothetical scenarios in which extremely tiny voltages or currents can trigger an unstable system.  This question intends to focus on realistically possible scenarios that could accidentally happen in everyday environments, e.g. in households.
Question:  In general, when should free-floating electrical contacts be considered potentially dangerous?  Danger may be direct (e.g., due to electrical shock) or indirect (e.g., due to fire risk).
Alternative statement:  Bob has an open circuit with two exposed contacts on his bedroom floor, built into into clothing (as part of some prototype wearable device he's working on), or in closet, pantry, desk drawer, or some other messy location where he/someone-else/misc.-items may come into contact with the electrodes.  The power source behind the electrodes maintains a potential difference of \$v\$ between them, up to a maximum current of \$i_{\text{max}}\$.  As a reasonably educated electrical engineer, Bob understands the potential danger of coming into contact with these electrodes.  Over the domain of voltages/current-limits \$\left(v,~i_{\text{max}}\right)\$, in what regions would Bob be:

unconcerned with any potential danger;

mildly concerned with potential danger;

worried;

reasonably certain something bad'll come of it?

Clarifications
Something is "dangerous" if any of the following apply:

Any person or pet coming into contact with the free-floating electrical contacts might suffer physical pain or/and any type of observable physical harm.

It's potentially possible for the electrical contacts to cause any sort of common household item to catch fire when exposed to the electrical contacts at length.

The electrical contacts could foreseeably cause observable damage to common household items, the house itself, etc..

As for risks:

I'm primarily looking for heuristics.  The goal is to separate "reasonable safety concerns" from "absurdly paranoid concerns".

Contrived risks may be omitted.  This is, I'm sure that we can come up with hypothetical scenarios, e.g. where the electrical contacts trigger a measuring device that intentionally starts a fire; however, I'm concerned with risks that might be accidentally encountered.

Risk-qualification's going to be fuzzy, and that's okay.  Perfectly valid answers may declare there to be a grey zones in which the presence-or-absence of danger is unclear/fuzzy.

The electrical contacts may be qualified by:

Being either AC or DC current.

Having any constant voltage between them.

Having any current-limit.

An ideal answer might provide a heuristic that a normal person could use to assess how they should feel about the potential danger from two exposed electrical contacts randomly scattered in their home of a known voltage-difference with a known current-limit for both AC and DC.


texts: Different LED for POWER ON and for LOAD ON, how to wire?

texts:
As you can see in the picture, for LED1 it's all good, 12v and 800 ohms = 15 mA to the led.

But i don't know how to wire LED2 since the load to the LED will change depending on the load/Vout of the supply. How can i wire LED2 in a smart way?

(I'm not gonna use this circuit, it's just for an example)

Update:
The reason that i wanted this from the beginning was because i wanted a way to break the load "fast". If i use a switch before LED1 and turn the circuit off, Capacitor C7 and C8 will have to be emptied and that will make the voltage slowly decrease instead of going to 0 directly. So i was thinking of having two switches like this:

And when the load switch is closed = current can flow then i want some kind of indicator (LED) in this case to light up and stay that way until i open the switch again, the lowest voltage possible is 1.25v, and the highest voltage in my case is around 18v. And i want the LED to stay on no matter what voltage i choose between 1.25 > 18v.

Also I'am a beginner in eletronics, so i apologize that i was a bit unclear. Please comment if you need me to add any more info regarding this.


texts: I was just wondering if there was a tutorial anywhere on how to make your own USB Flash Drive and I don't mean take apart a USB and put the guts into something else, I mean put together the flash memory and controller.


texts:
I'm working on a RF 4 layer PCB that includes RF switch (PE426412). This Ic is controlled by 4 digital pins.These digital signals differentially come from out of the board and by ADM485ARZ converts to a single.
I don't know if my circuit needs further filters or any other thing that I should be concern about.

Thank you to help me find the answers.


texts:
The above is the requirement, I have configured a circuit as shown below

simulate this circuit – Schematic created using CircuitLab

I have solved the above schematic using superposition and deduced that \$R_1:R_3 = 3:1\$, but I could not get the required output.

Superposition node voltages:

When \$V_1 = 0\$, $$V_{\text{node}} = \frac{R_2V_1}{R_1+R_2+R_1R_2}$$

When \$V_2 = 0\$, $$V_{\text{node}} = \frac{R_1V_2}{R_1+R_2+R_1R_2}$$

I have mapped the coefficients and deduced the above ratio.


texts: I'm looking to create a simple circuit that will have 8 randomized "pulsing/fading" LED's

texts:
I am looking to make a simple (cheap, small spaced) circuit that will light 8 LEDs in a random order AND have a pulsing/fading in and out effect. I was originally going to program a randomized effect, but I found a schematic using a 4026 counter and display driver and 555 counter that will do the deed instead (saving time and hair pulling). The problem I am having is figuring out how to get the fading effect on each LED and how I would implement that with the randomized effect.

The circuit I found is here: http://rookieelectronics.com/sequential-random-led-flasher/.

I know that changing the capacitor value will slow/speed up the blinking speed, but won't add the fading effect I'm looking for. My best guess is either attach another capacitor between the LED and driver, or to implement a BJT into the circuit. I'm pretty stuck so any advice would be great!

I should also mention I plan on making this DC with a 6V battery. It can be higher voltage if needed, that was just the original plan.

Thanks and have a great day!


texts: Number of machine cycles in microprocessor 8085

texts: The DCR instruction in MP 8085 has has 1 machine cycle, i.e. opcode fetch cycle. But the DCR M instruction has 3 machine cycles. What are those three machine cycles?


texts:
I'm developing a printed circuit board, and considering I have some traces with 220Vac I'm worried about the clearance.
After research, I conclude that these are the requirements that I need to fulfill:
Voltage (peak) = 350V, according to IPC-2221B:

External Trace -> 2,5  mm
Internal Trace -> 0,25 mm
Coated Trace -> 0,8  mm

The application is for normal conditions, 25°C Ambient Temperature.
In the manufactured boards, like the below, can I consider the traces coated?

(source: pcbway.com)


texts: Step Down 12v to 5V Battery powered supply [LOW COST]

texts:
I have battery source which provides 12V supply and I need to feed 5V to the MCU.
The electronic in which it will be use, will be running continuously for 10-12 hours per day. I have very less current requirement of around 100 mA.

The battery has high capacity as used in motorcycle. So battery life is not of much issue. But the heat dissipation is.

I am planning to use L78L05 positive regulator from ST. Here is the part :

I could have use the switching regulator but it will be expensive, I have to keep BOM cost as less as possible. So is it a good idea to use above part? Any other part can I use?

I know the heat dissipation will be higher when using the linear regulator, but using switching regulator will make huge impact on the cost.

Any other alternative to step down supply from 12V to 5V with less heat dissipation and low BOM cost.?

Thermal Data of the part :


texts:
I have come across a handful of examples of PID controllers where the process input is the accumulated PID output, i.e. the controller loop is u += pid(...) rather than u = pid(...) where u is the process input.

For the sake of example, say we are using PID to control the speed of a motor via PWM,

class PID:
    def __init__(self, kp, ki, kd):
        self.kp = kp
        self.ki = ki
        self.kd = kd

    ...

    def pid(self, set_point, process_variable):
        now = time()
        dt = now - self.last_time

        error = set_point - process_variable
        p = self.kp * error
        i = self.ki * error * dt + self.i_sum
        d = self.kd * (error - self.last_error) / dt
        output = p + i + d

        self.i_sum = i
        self.last_error = error
        self.last_time = now

        return output

My understanding of PID is that we should use the controller as

pid = PID(kp, ki, kd)
...
motor_pwm = pid.pid(target_speed, measured_speed)

But I often see it implemented as

pid = PID(kp, ki, kd)
...
motor_pwm += pid.pid(target_speed, measured_speed)

Now, for ki = kd = 0, the latter makes some intuitive sense to me; in fact, I think it actually gives you a kind of PI controller with ki = kp, and dt = 1 enforced. Once you introduce ki != 0 or kd != 0, however, I can't square this with any of the textbook explanations of PID I have read.

Is this 'accumulated' u += pid(...) controller simply an incorrect implementation of PID?


texts:
I am making a digital weighing scale circuit and currently having difficulties understanding filters that are commonly used to reduce noise in these type of circuits. My load cell is a full-bridge with a max-capacity of 200kg and 2mV/V rated output. With an excitation voltage of 5V, I am only amplifying half the signal (0-5mV) using an AD620 in-amp. Then I used AD822 as difference amplifier to subtract an offset of 2.47V and then amplify it again by 4.9 to have an output swing of about 200mV to 4.8V.

My questions are:

1) Is the headroom voltage I have provided for the ADC large enough or actually small? Because I have read that its a common rule to provide a headroom for your ADC but I don't know exactly how much so I settled with 200mV. I am using the built-in ADC of arduino(10-bit resolution)

2) As you can see, I am using the basic way of constructing  a difference amplifier and non-inverting amplifier with my AD822. Is there a more effective way of doing this? Or is there something I need to add to make my output more stable and accurate? Because on the diff amp, I'm actually having a pretty stable output but with regards to my non-inverting amp, it is having some inaccuracies, e.g. instead of having an output closely at 196mV at 40mV input (40mV * gain of 4.9 = 196mV), I'm having an output of something like 230mV. And also it is varying unexpectedly with non-moving load.

3) Sorry for this but i basically don't know something about filtering noise. What are your recommendations for my circuit on filtering noise? I think i must have to put something between my load cell and AD620 in-amp, and between my non-inverting amp and ADC but I don't know what exactly they are right now.

All kinds of help are greatly appreciated!

FYI, decoupling caps were used on each IC but were not indicated on the schematic below. (0.1micro paralleled with 0.33micro)

And if this could help, this is my code for testing my values, it is actually the sample code provided for smoothing analog values.

  total= total - readings[index];

  readings[index] = analogRead(inputPin);

  total= total + readings[index];

  index = index + 1;

  if (index >= numReadings)

    index = 0;

  average = total / numReadings;

  Serial.println(average);

  delay(500);


texts:
I have some Amphenol 24AwG Spectra-Strip 10 conductor ribbon cable that I want to use in an aquarium LED project.

Unfortunately, its dimensions don't match those of a traditional 2x5 crimp connector. The spacing between the individual conductors is such that only half of the ribbon fits within the connector.

Does anyone know of a source for ribbon cable crimp connectors that work with larger size ribbons? If not, what other approaches could I try?

Additional Info

From what I can gather, for 2xN ribbon cable crimp connectors, the spacing between wires has to be 0.05 inches, even though the connectors themselves present the pins on a 0.1 inch interval. My 10 conductor ribbon cable has the individual conductors at 0.1 inch intervals, so a typical 2x5 connector only connects 5 of its pins when it's crimped on (the other five slots "connect" to the ribbon material between each conductor).

It occurred to me I could work around the problem of using this particular ribbon cable by using a standard 2x10 connector. Only half of the pins will be connected to a wire, but that would least let me use standard parts.

I've ordered some 2x10s and will report back on what I learn.


texts: how to use a 3v output to control a 5v relay

texts:
I have some circuit where my board (Electric imp) can output up to 3.3v,
and i need to control a relay with atleast 5v in order to effect the coil and close the circuit.
i have a power supply of 5v, so i was thinking maybe using a transistor with gate connected to my 3.3v signal, and somehow to control the transistor to push the 5v power supply to the relay.

but how? the only idea i had is making an inverter, wiring 5v to pmos, pmos drain to vout, and also nmos to drain and from there to GND.
and then when 3.3v -> vout = 0, and when 0v -> vout = 5v.
not exactly 5v, because i i need to know Vsd


texts: Voltage gain from the Amplifier input to the load

texts: I don't understand where the solution for part C coming from. What I thought is also Vo/Vi. I found Vo as 303 mV and Vi as Vs*(10/10+100). However in solution it seems my thought is wrong. How should I think?


texts: Switch on off using triac BTA24, When off keep flashing LED lamp

texts:
Friends have a simple circuit a switch on off using triac BTA24600B, The strange fact is that when I turn off my led lamp keeps flashing fast, this is not the case with other types of lamps, only with LED lamps, the problem is only when it is Off when turned on works perfect. Has anyone ever experienced this?

https://www.youtube.com/watch?v=YgOwgLLlSvw&feature=youtu.be


texts: What's the junk at the end of my FFT in LTSPICE?

texts:
Why do FFTs have junk on the high frequency end? Suppose I go to simulate this circuit in LTSPICE:

simulate this circuit – Schematic created using CircuitLab

Where the LTSPICE sine and simulation parameters are:

SINE(0 1 1K 0 0 0 1000)
.tran 1 startup

Then I ask LTSPICE to give me an FFT with no window and 1,000,000 points:

What's all the junk at the end for? I would expect only one spike at 1KHz, not an additional one at 3KHz, etc. Does this happen to all FFTs? What controls the spikes that you get after your fundamental?


texts: How do I work out what temperature to use when desoldering?

texts:
I have a temperature controlled soldering station, and know that I need to set the temperature appropriately for soldering based on the solder I use when soldering, but how do I determine what temperature to use when de-soldering components from a commercially manufactured PCB?

So far I have just been using 400°C and been careful not to heat for too long, but searches here on electronics and on the wider web have not been able to tell me how to work out what the ideal temperature for de-soldering would be.


texts: Does pin order matter at all for this RAM?

texts:
I am trying to route a pic32 chip to a 128kB SRAM chip and having a bit of a hard time getting all 17 address lines and all 8 data lines connected. I am trying to tie the first 16 address pins to portB pins 0-15 and the data pins to portD 0-7.
After thinking about it for a while I realized that I am probably making my life more difficult by trying to line up rb0 with a0, rb1 with a1, etc. All I really want to be able to do is write a 16 bit value to portB and have the majority of the address loaded and ready. If I make pin assignments based on ease of routing, the logical address will be different between the mcu and the ram, but it should at least be consistent. Since nothing else needs to communicate with the RAM, I don't think it will be a problem if the mcu asks for address 0x101 and the RAM gives it address 0x110.

However, I wonder if it is a good idea. If there is some structure internal to the RAM designed to make sequential reads more efficient, or something like that, then I may want to go to the trouble of routing them 1:1. The pins arrangement on both chips fees somewhat random to me, so it would make it a lot easier on me if I could ignore the particular numbers. Is there any good reason why I should or should not do that?


texts: Building a 2's complementer (need help visualising how to make a state diagram and table)

texts:
Just to be fair, this is a previous exam question and was an assignment question. I've already handed in the assignment and now I'm trying to see why I got it wrong -- to study for my final.

I fully understand how to find the 2's complement of a binary number, however, implementing a circuit to find the complement is driving me crazy. I'm given a shift register (that stores my binary number) and a flip flop (using D for simplicity). The process I follow for building sequential circuits is this:

I look at the question and derive a state diagram.
From the state diagram, I draw a state table and find the input of my flip flops
I use maps and stuff to finally build the circuit.

I'm trying to visualize how to actually draw the state diagram for this complementer. I know it depends on the previous value and stuff, but if someone could take the time to explain in plain english how he/she would go about building the state diagram, I would be vey grateful.


texts:
What is the difference between add stitching to net and add shielding to net ?

In my understanding in both case it create via to shield some part of the cricuit...


texts: Converting 24VAC to 5VDC - Need transformer demystification

texts:
I've got an automatic litterbox that 'needs' to be hacked for better control. As it ships, it comes with a 120VAC to 24VAC (300 mA) wall wart that drives the two motors in it. I'm trying not to change out the original power supply, as I don't want to change the motors.

What I'm looking to do is get 5VDC for a microcontroller. My first thought was to simply toss a rectifier circuit and a 7805 and I'd be done. However, it seems that the 7805 wants a max Vin of 20VDC. Next thought was to find a small transformer to step the 24VAC down to around 12VAC and then pass that to the rectifier and 7805.

To that end, I started looking around for a transformer that I could use. Sensibly enough, everything I can find seems designed for a 120VAC primary. I came across this small tranformer, which I'm guessing is an audio transformer.

Am I right in presuming that the resistance of each coil is directly proportional to the number of windings? Thus, if I were feed 24VAC into that transformer with a primary of 115 Ohms and a secondary of 69 Ohms, I think I would get 14.4VAC out. Is that correct? Also, can I get away with using what is probably an audio transformer for this purpose?


texts: How much can BJT parameters (particularly beta) vary for Monte Carlo analysis

texts:
Background / Requirements:

I'm designing a typical Class AB amplifier using diode-connected BJTs to achieve the biasing. I have a requirement to keep the total quiescent current at room temperature to less than 8mA (from a single rail). Additionally the amplifier has to reliably source 100 mA \$AC_{pk}\$ to a \$100 \Omega\$ load over the industrial temperature range of \$-40^\circ C\$ to \$+85^\circ C \$. Here is the current rendition of my schematic:

simulate this circuit – Schematic created using CircuitLab

My Problem:

The resistors R4 and R5 have to be sized such that they can supply the maximum base current required by Q1 and Q2. However, I cannot have R4 and R5 too low due to my low quiescent current requirement.

I don't know how much the base current on the BJTs can vary. Before you step in and give the usual answer--"a lot" (which may very well be the case), let's look at what I have so far. I'm using the On Semi NSS40302PDR2G complementary NPN/PNP. Let's just consider the NPN case for now:

The TYPICAL \$\beta\$ is 350 and the MINIMUM \$\beta\$ is 200, both specified at room temperature and \$iC=500 \$ mA. Based on this information, what would I expect the MINIMUM beta to be at \$-40^\circ C\$?

Based on the temperature-dependence formula SPICE uses:

$$\beta(T_1) = \beta(T_0) \left[ \frac{T_1}{T_0} \right]^{XTB}$$

Where XTB can be obtained from the SPICE model (for the NPN transistor, XTB = 0.437188). We can calculate the expected MINIMUM \$\beta\$ at \$-40^\circ C\$ and \$i_C=500\$ mA:

$$\beta(-40^\circ C)_{min} = 200 \left[ \frac{273.15 - 40}{300} \right]^{0.437188} = 179$$

I can live with a worst-case \$\beta\$ of 179. Now, \$\beta\$is obviously not the only parameter to vary in a BJT. Let's look at Is and NF. From the datasheet we see that \$v_{be(on)}\$ at 100 mA is typically 0.65V but has a maximum of 0.75V at room temperature. Let's see how the collector current changes with Is and NF (the non-ideality factor)

$$i_c = I_s \left( e^{v_{be(on)}/(V_T N_F)} - 1 \right) - I_s$$

Now, solving for Vbe(on):

$$v_{be(on)} = N_F V_T \ln \left( \frac{-i_c - 2 I_s}{I_s} \right)$$

Now, let's make \$N_F\$ and \$I_S\$ be variable by some tolerance, TOL (in %):

$$v_{be(on)} = N_F(1 + TOL/100) V_T \ln \left( \frac{-i_c - 2 I_s (1+TOL/100)}{I_s (1+TOL/100)} \right)$$

Setting tolerance to zero and plugging in the 100 mA for \$i_C\$ and the remaining parameters pulled from the SPICE model gives a \$v_{be(on)} = 0.655\$ (close enough to the datasheet that I believe it).

Now how much TOL do we need to reach the 0.75V stated as the MAXIMUM in the dataseet? Solving with mathematica gives:

$$TOL \rightarrow 15.3171$$

That is, both Is and NF can vary by 15% according to the datasheet. Now we get the the Monte Carlo analysis. In order to show that my circuit above works over device variation and temperature, I am performing Monte Carlo analysis in LTSPICE by varying all the BJT device parameters by 15% and Beta by 75%. This gives me huge base currents for some cases (much more than anticipated by the \$\beta = 179\$ calculation).

Am I being too hard on myself?
By varying the device parameters by 15% over temperature, some cases give me a Beta <20. Which for most BJTs would be expected, but I specifically chose the On Semi NSS40302PDR2G for the seemingly excellent Beta.

Hopefully answerable Questions:

Is my 15% device parameter variation using monte carlo analysis
too harsh? Is the \$\beta=179\$ calculation at all likely?
If answer to (1) is "No, you will actually see \$\beta < 20\$ after
building many circuits", then any ideas on how to modify this
circuit to make it more beta independent without adding many (if
any) components?


texts: When an NMOS utilizes a PMOS current source load, which transistor is acting as the current source?

texts:
Referring to the following schematic:

My current understanding dictates that a transistor will output a certain drain current given an input voltage at the gate (V1 and V2). How can this behavior stand true in the schematic shown, since there will be two "competing" current sources? Which transistor sets the current of the circuit?


texts: what is maximum Input voltage for 2s bms

texts:
I am making UPS for my 12v broadband router. I am planing to use XL6009 boots converter to booter 8.4 volt to 12v. For charging 2s Li-ion battery with 2s BMS i don't have 8.4v charger. Can I use 12V or 9V 2AMP DC adapter to charge my batteries.

I am using this BMS


texts: Why the unusually high "LOW" voltage when pressing NodeMCU ESP-32s boot button?

texts:
I bought a ESP-32 development board and I'm having a lot of trouble with a button on the GPIO00 pin. This is a strapping pin on the ESP32 chip; when set to LOW on startup, the chip enters the bootloader. There's a convenient button on the development board.

In the schematic for the dev board, there's a 12k pull-up resistor between GPIO00 and 3.3V, and 470ohm between GPIO00 and the button; the button connects to ground. I confirmed this with my multimeter. Given that, I'd expect to read 0.12V when pressing the button. Instead I read 1.33V! This is outside the spec for the low-level digital input, though it seems to enter the bootloader properly.

Does anyone know why there's such a high voltage when pressing the boot button (GPIO00)? Is there anyway to mitigate this if I want to connect my own button to GPIO00?

Schematics for NodeMCU ESP-32S:


texts: Why do we use negative edge trigger Flip Flop instead of positive edge triggered?

texts:
The glitches due to race condition can be avoided by using a negative-edge triggered flip-flop instead of the positive-edge-triggered flip-flop used.

What does this mean?

Source: http://www.zeepedia.com/read.php?the_555_timer_race_conditions_asynchronous_ripple_counters_digital_logic_design&b=9&c=26


texts: I am fairly new to electronics, and I got a NodeMCU 0.9 ESP-12 for my IOT Projects. I want to power it through the wall, and I have an adapter which outputs 5 Volts and 2.5 Amps. Is it safe to connect this to USB to my ESP-8266?


texts: Inferring common mode impedance for a given CMRR

texts:
In the figure below, the common mode impedances of the line driver and receiver are represented by RCM+ and RC-:

(What I understand by the phrase CM impedance is that it is the resistance or impedance seen by the common mode voltage.)

This CM impedance parameters sometimes are not given in a datasheet directly.

If the CMRR of an amplifier or a transformer ect. is given as 100dB at a particular frequency can we estimate the common mode impedance?

Since -100dB is 10^-5, can we than say the common mode impedance is 100k Ohm?

For instance in this module data-sheet in the second page at specifications, the CMR, the NMR and the input impedance/resistance are explicitly given. Can we also estimate the common mode impedance as well?


texts: What is the difference between signal and symbol in wireless communications?

texts:
What are the definitions of signal and symbol in wireless communications, respectively? Often when I read books and papers I see things like "transmitted signal" and "transmitted symbol". Is there a difference? I tried searching online, but most results treat them as just words in English, not as concepts in wireless communications. I am new to this field and I'd appreciate any help.

For example, in the paper Beamforming Design for Large-Scale Antenna Arrays Using Deep Learning by Lin and Zhu, the words appear in the same paragraph introducing the system model:

  Let s denote the transmitted symbol with normalized average symbol energy,
  i.e., E{|s|^2} = 1. The symbol is first multiplied by a scalar digital precoder v_{D}, and then by an Nt × 1 analog precoder v_{RF}, which is implemented using phase shifters. The final precoded signal is then given by x = v_{RF}v_{D}s.


texts: Are varicaps (capacity diodes) obsolete?

texts:
I have read that varicaps (capacity diodes) are a "modern" alternative to variable capacitors. In several electronics books only positive properties of varicaps are mentioned.

But several major distributors (here in Germany) simply don't offer varicaps, or just have less than 5 of SOT-23 models. (For comparison: same distributor offers around 1000 different diode models.)

At three largest German distributors of electronic components I couldn't find a single DO-xxx case varicap. Only SOT-xxx.

Does it mean that varicaps are obsolete? If so, what do people use in today's circuits as "replacement"? Or, more general, is there some more common "concept" to vary capacity?

Thank you.


texts: Active (P), Reactive (Q, D) and Apparent (S) Power from Instantaneous Power (p)

texts:
I am having a difficultly with producing \$S, P, Q \$ and \$D\$ from Instantaneous Power \$p(t)\$.

Let's say that both voltage and current are clear sine waves. Then:

\$p(t) = Vsin(ωt+φ_V) \cdot Isin(ωt+φ_I)\$

and by using the identity

\$sinA sinB = \frac{1}{2} (cos(A-B) - cos(A+B)) \$

instantaneous power can be written as

\$p(t) = \frac{VI}{2}cos(φ_V-φ_I) - \frac{VI}{2}cos(2ωt+φ_V+φ_I)\$

Now, it can be proved that at a pure sine wave \$A_{RMS} = \frac{A_{peak}}{\sqrt2} \$, hence:

\$P = V_{RMS}I_{RMS} \cdot cos(φ_V-φ_I)\$.

How to prove that \$Q = V_{RMS}I_{RMS}\cdot sin(φ_V-φ_I)\$ and \$S = V_{RMS}I_{RMS}\$?

Moreover, how to prove that

\$P = \sum_{k=1}^\infty V_{RMS}I_{RMS} \cdot cos(φ_V-φ_I) \\ Q=\sum_{k=1}^\infty V_{RMS}I_{RMS} \cdot sin(φ_V-φ_I) \\ D = \sqrt{\sum_{k\ne j}^{\infty} U_k^2I_j^2 +U_j^2I_K^2 - 2 U_kI_kU_jI_jcos(φ_k-φ_j)}\$

when voltage and current are not sines, but arbitrary, periodic waveforms?

I don't expect from anyone to  provide me with the full proof, but to show me the right direction.

EDIT:

In order to prove that \$Q = V_{RMS}I_{RMS}\cdot sin(φ_V-φ_I)\$ - for pure sine waves - one must analyze the current to two components. One that's in phase with the voltage and one that's \$\pm90^o \$ out of phase. By drawing the phasors \$\vec{V}, \vec{I_X}\$ and \$ \vec{I_Y}\$ this becomes obvious.


texts: Working of NAND gate using diodes and transistors

texts:
I found this circuit which is used to construct a NAND gate. Although I understand the working of AND, OR, and NOT gates constructed using diodes and transistors, I just cannot understand the working of this NAND gate circuit at all. Any help would be highly appreciated.

P.S. : What is the function of the diodes D3 and D4 shown in the diagram?


texts: Can I (mis-)use my USB-to-parallel (printer) cable as UART cable in some way (e.g. sticking some cables in the female parallel output and use them as UART connectors)?