texts: How can I read/write bytes to SD card slot of MC60A?

texts:
I am working on a clickBoard with MC60 A GSM module from MikroEletronika company.

This clickBoard has two slots: (1) one for SIM card and another (2) for micro SD cards. I have read all the available documentation: AT commands  user guide manual (Quectel documentation) and some code examples (Libstock) and i still cannot find any information about how can I communicate with SD card slot.

The only thing I've found about this topic was on quectel hardware guide:

  The following are the main features of SD card interface:
  - Only supports 1bit serial mode; Not support the SPI mode for SD memory card
  - No support multiple SD memory cards
  - No support hot plug; The data rate up to 48MHz in serial mode
  - Support for memory cards with maximum capacity up to 32GB;

From this I assume it is a serial communication. So, with the info I know, the two questions I have are:

Can I write/read bytes with the usage of AT commands? If yes, which AT commands?
It is necessary any specific format for micro SD card (FAT, exFAT, FAT32 or NFTS)?


texts:
I've just started doing some work for a company doing some CAD work where they use Altium 16. (16.1.10 to be precise.)

I've used umpteen CAD systems over the years, but done very little Altium. I want to change the colours in the schematic, most especially so I have a black background. Now, changing the background to black is easy. However, I cannot find where you then change the colours of the nets, symbol bodies, pin numbers etc etc.

There surely must be a way of doing such a basic thing on what purports to be a very powerful CAD system. In fact if you can change the background to be black, you surely must be able to change everything else from being black. Otherwise you have a black symbol on a black background saying "do not click." (*)

No-one else here has tried to change from the glaring white background, so they can't help me. An hour or so of Googling has found me nowt either.

So, how do I change my colours so I can have green nets, red symbol bodies etc please?

- * With apologies to Douglas Adams.


texts: I am attempting to make a smaller coil gun (pistol). I do not have a super capacitor. However, I have about x400, 10v, 2200uF capacitors. Am I able to make a bank of a sort and get the same effect as a large capacitor with many small ones?


texts: Digital Circuit with Toggle Switch using Logisim

texts:
I'm supposed to design a small digital circuit (with Logisim) using basic logic gates, so that when this circuit is used with the chosen switch (which has to be a button), it will make the circuit function as a toggle switch.

So when I press the button it turns on the LED display(the output) and when I press it again it turns off.

http://imgur.com/H0lgj1c is what I've so far but it's not working and I don't seem to understand why. Can someone please help me out?

Thanks


texts:
I am new to electrical engineering and I am trying to run an n-channel MOSFET (this one) as a PWM switch to a motor. Following some tutorials online I have this setup for my circuit.

simulate this circuit – Schematic created using CircuitLab

When I try to run this circuit, even with no input to the gate, the motor always runs and the MOSFET heats up. The source-drain voltage is 30 max and I'm only running 24V.


texts: How to design an electric circuit that makes an LED light flash at 50 Hz

texts:
I have a record turntable in which the correct speed of rotation is obtained by adjusting the speed until a pattern of black/white lines on the outside edge of the platen appears stationary.

Currently a neon light flashing at mains frequency (50 Hz) shines onto the rotating pattern. It is difficult to find a replacement neon bulb and it is too dim. Hence I would like to replace it with a better system. I believe an LED light flashes at 100 Hz using 50 Hz mains.

I would be very grateful for a solution to the problem!

Thank you.
Elner


texts: Bluetooth receiver from multiple transmitters

texts:
I need a bluetooth receiver to receive a signal from few transmitters. There is extremely little information about bluetooth on the internet. Google gives a lot of topics about android and iPhones, but that is not what I am looking for.

What if we will take something similar to this one: BT0415. Is it even possible in theory?

If you will prompt me which way to dig, I will be truly grateful for you.

Here is a small pic of what I really looking for.

Edit: Forgot to mention, that the real problem is that receiver should be smaller than transmitters. So it is impossible to put few receivers in one box.


texts:
Can an insulated wire be used to make a electromagnet? Will there be any difference in strength of the magnet if I use an uninsulated wire instead?
By uninsulated wire I mean this:


texts: Converting analog 10-bit thermistor reading (MCP3008) to temperature

texts:
I'll start by explaining my circuit:

First of all I'm using a Raspberry Pi and the MCP3008 chip on a breadboard. I have 3.3 V going to my thermistor (\$1 k\Omega\$ at \$0^{\circ}C\$) when it returns I have a \$1 k\Omega\$ resistor that goes to ground, and a wire that goes to the MCP3008 chip.

I'm reading the resistance kind of fine using the chip by using this formula:

$$R = \left(\frac{1023}{reading}-1\right) \cdot R_{0^{\circ}C}$$

e.g.

$$R = \left(\frac{1023}{510}-1\right) \cdot 1000 = 1009.82~\Omega~~at~0^{\circ}C~(ice~water)$$

I've been reading about Steinhart and Hart last night, but I simply can't get a formula that works for converting this into a temperature. I even have a spreadsheet showing values of resistance for different temperatures of the thermistor: Pt-1000 Resistance Scheme

I would really appreciate if someone could show me how this conversion is done, and also if I can get a more precise reading, that would be amazing.


texts: Can we ground all the nets in a printed circuit board?

texts:
I am a newbie in electronics and I am designing a printed circuit board.

The IC I am using has some pins that I don't use in my circuit. Is it okay to ground those nets or leave them as they are?

I am  asking this because I have heard that sometimes these nets can act as floating pins and could cause noise and errors. I am not sure whether this is true or not so please clarify my doubt and suggest me the right way.


texts: Blinking LED at two different frequencies

texts:
I am trying to build a circuit that will make a LED to blink at a certain frequency, probably by using 555 timer.
As the circuit will be supplied by a 3 Volt battery, so I want to extend a feature that LED should start blinking at a higher frequency indicating low battery status but I dont know how to add this feature to the circuit without adding any other IC or comparator.

Any help is greatly appreciated.


texts:
I am currently using a SHARP GP2YOA21 infrared distance measuring sensor which is 5.0V. I am looking for an alternative IR sensor that would work with 3.3V.

Our application involves wireless sensor network, energy harvesting, etc.

Does anyone know any alternative?


texts: Why does the l293 have a higher current than the l293D?

texts:
I know the "D" mean diode, so it has a built in diode. I would not think that the addition of a built in diode would lower the current rating by that much. Also, if I were to use a l293, where would the diodes go and in which orientation (I am driving a bipolar stepper)?

Also, would I be able to increase the current rating of the l293D somehow? I really don't think putting them in parallel works, even though many people say it does. The datasheet doesn't say if it is a FET or transistor based system, but I suspect it is transistor based.


texts: Is it bad to leave a filter capacitor floating?

texts:
The circuit detail presented is a gyrator filter that is one of two that hang out in the feedback loop of an opamp, creating a "low" and "high" tone control for audio. (The "low" section is shown) I'd like to have two available boost/cut frequencies for each control, though. It's easy enough to switch an extra set of paralleled caps as shown and breadboard tests are so far successful, but I've never seen it done this way. Is there a demon lurking in the floating capacitors?

And does it really matter which "side" of the caps the switch is on?

simulate this circuit – Schematic created using CircuitLab

and here is where i found my example in it's natural habitat: http://electricdruid.net/wp-content/uploads/2016/01/Boss-MT-2-Metal-Zone-Schematic.pdf

I know, I know, it's a guitar stompbox...but just in case it helps to see the "low" and "high" tone section in some sort of context. In this schematic, the "low" section is built around an opamp, whereas my example circuit above shows a BJT as the active. I did this to draw the example faster.


texts: How to protect Microcontroller from any damage if there is motors and sensors on PCB

texts:
I am working on a robot PCB , I am using 3 DC motor with DRV 8871 motor driver IC and 6 ultrasonic sensors and a microcontrollerCC1350 , I don’t want to damage my MCU from any spike or other factors thats why I am using RecomDC-DC isolated converter and optocoupler for isolation of MCU from sensor & motors  I am powering whole PCB with LiFePO4 battery .
my concern is that can I I make this simple ? can I directly use microcontroller (with sharing ground no isolation ) or I am taking too much safety precautions

Motor operating voltage +24 V
Sensors operating voltage (10-30V)
Battery voltage 25.9 Volt 10Ah


texts: Isolated MOSFET output stage calculations

texts:
I am a newcomer in this wonderful world of electronics trying to design my own PLC.

So far I have designed a single output stage that I think will work, but it would be great if i could have any of you experts confirm my thoughts and calculations..

I have selected the following components (mostly based on lowest cost at RS components):

74HC595 shift register
PC357N14J00F optocoupler
DMP2160U-7 P-Channel MOSFET

The shift register can source 6 mA and the IR LED in the optocoupler have a forward voltage of 1.2 V. R1 should then be (5-1.2)/0.006 = 633R (680R)

The collector-emitter voltage of the optocoupler is 0.1 V when fully saturated, the LED has a voltage drop of 1.2 V. To drive the LED at 20 mA, R2 should be (12-0.1-1.2)/0.02 = 535R (560R)

When no current is driven through the IR LED in the optocoupler, the gate of the MOSFET will be pulled high by R2. When the output is enabled the gate will be pulled to 1.3 V which would bring Vgs to -10.7 V and thus turn the MOSFET fully on.

Questions:

Are my calculations/assumptions correct?
How do I know whether the transistor output of the optocoupler is saturated
or not?
Do I need any other components in order to protect the output stage?


texts: Is "Peak NMOS current limit" the continuous output current limit of this LED driver?

texts:
I am trying to find the maximum current the DIO5661CD6 can supply to the LED(s.) I do not see the usual "continuous current" parameter anywhere in the datasheet.
Is the "Peak NMOS current limit" the one I need?
From page 4 of the datasheet:

If yes, why is it labeled "NMOS current"?


texts:
I am computing Johnson and shot noise in a DC circuit, where I have an Arduino Due sampling with "delay(100);", i.e. at 10Hz.

Sampling rate and bandwidth follow Nyquist sampling theorem. According to this theorem, the sampling rate should be at least twice the bandwidth of the input signal. Since our sampling rate is 10Hz, the bandwidth should be $$5\text{Hz}.$$
Is this correct? Does this mean that many sources of noise just disappear if I add a large enough delay to my code? What is the correct answer for the bandwidth?


texts: How is the frequency division using logic gates on this old video card happening?

texts:
I am trying to understand how the main crystal on a (very) old IBM MDA videocard, running at 16.257 MHz is being divided into lower frequencies like the 1.80633 MHz that its main display controller chip (MC6845) expects as a clock.

As you can see from the schema below, something needs to convert the 16.257 MHz clock from the crystal down to a 1.80633 MHz character clock that is fed into the display controller (the display controller chip will then calculate the hsync / vsync / .....). So focus here is on how to get from 16.257 MHz to 1.80633 MHz

There are lots of logic gates in the circuit, and although I have found the schemas for the card online I am lacking some understanding on how to interpret what is going on.

I've been told that the 74LS174 (U1) is responsible for that, and I am indeed seeing both the 16.257 MHz (pin 9), and the 1.80633 MHz (pin 3) when using my multimeter, but I don't understand how it is doing the actual division.

I know that in the circuit 5 D-type flip flops in the 74LS174 are being used, where each output is fed back into the next flip flop input, but I don't understand how it works especially the 3.612 MHz ( = 16.257 / 4.5) I am seeing on all output pins and the 1.80933 MHz on the first flip flop input pin (pin 3). For that input some kind of feedback loop is used involving an LS32 and LS10.

Does this construct have a name, and how can I go about understand more on the inner workings of this thing.


texts:
Disclaimer:

I hope that I have not carelessly overlooked a previous post that answers this question; but I definitely have tried, and still find myself a little lost.

Situation:

I have 15 A123 ANR26650M1A batteries connected in series. They have a safe maximum continuous charging current of 10 amps, which is stated to have a fast charge time of 15min. I am about to purchase a programmable active balancing BMS board based on the MAX14921. I also have a Mean Well RSP-1000-48 that supports up to 21 amps. Currently, I have been balance charging my series, with a variable DC bench power supply, with a constant current of 10 amps, and constant voltage at 54 volts, through a PCM board for top balancing. The bench PSU is not charging anywhere near 10 amps, and I am not getting anywhere near 15 minute charging times.

Aside from that, most importantly, when I order the programmable BMS, I want to be able to achieve a charging time of 15 minutes utilizing the Mean Well PSU. I cannot seem to find anywhere that explains how this is achieved.

Questions:

Why am I not able to charge the battery with the variable bench power supply at a constant 10 amps?
How do I charge the 15 batteries connected in series at a constant current of 10 amps through the programmable BMS with a Mean Well PSU? Does the BMS basically get programmed like a programmable charger? Is there some other hardware I may be missing?

I've included links to all of the other datasheets I could find for these cells as well.

Battery Pack Design Safety Guidelines
Proper Operation of A123Systems High Power Lithium-ion cells has
an actual section titled 'recommended fast charge method'

I apologize for my ignorance, and thank you in advance.


texts: EAGLE for 10 layer boards with 337-ball BGA?

texts:
I have been using EAGLE for some years. The boards I have designed had the following specs:

up to 4 layers
6mil spacing
densest package: QFN, 0.4mm pitch
only "ordinary" vias
mainly (low frequency) digital domain (CAN, IO, ...)

The new project has this specs:

up to 10 (or even 12) layers
densest package: 337-ball BGA (ARM-Cortext-R5)
potentially blind and/or buried vias

My concern is: Is EAGLE sufficient for the new project? Or should I consider to switch to a more "advanced" PCB design tool, like Altium designer, Mentor Graphics Pads or Cadence Allegro?


texts:
I'm a college student learning the basics of NFC loop antenna design.

As a starting point, I'm trying to design a PCB-based rectangular NFC loop operating at 13.56 MHz, matched to 50Ω.
(NFC "inductive" loop -->> matching network -->> SMA connector).

I plan to produce two antennas, and after fabrication, I'm planning to test these by making these two "touch" and see its reaction/performance through a Vector Network Analyzer
I've read quite a number of application notes, and currently have some questions in mind. I hope someone can help me with these:

Can I make the the two antennas ("reader" and "tag") identical (same geometry, etc)? Or should I make the tag antenna smaller?
Since, I'll be using a VNA to examine its performance, I need to match the loop impedance to 50 Ohms. I'm currently planning to do it using discrete R and C components. Is there a better way to do it? (I mean, discrete and surface mount R and C are available in standard values, I'll be having a problem if my required R and C matching components have values far from standard.)
The loop has two "ends". One terminating inside the inner loop, and the other outside the outer loop. I need to connect both of these to the SMA, right? Does it matter which end connects to ground and which end connects to the signal?
I'm planning to use HFSS to simulate my design. Are there any specific reports/tests I should examine before implementing the design?
Can you recommend appnotes and articles that I can further read and study to help me with my goal? (URLs with a good discussion on Basic NFC loop design)

I hope someone could guide me.
Thanks a lot!


texts: What are some major considerations for having an accurate ADC (SAR type)?

texts:
What are some factors considered to ensure a SAR-type ADC is accurate on the hardware level?
Some things I think are relevant:

Buffering the ADC inputs
Voltage reference accuracy
Having an accurate oscillator for the processor

Would there be any other major considerations?
The assumption would be for someone using any commercially-available SAR-ADC chip and not designing the ADC circuit itself.


texts:
I was reading Morris Mano's - Computer System Architechture and My problem is the simplification of F = AB + A'C which was:

simulate this circuit – Schematic created using CircuitLab

which was simplified to:

simulate this circuit

I am confused why NOT1 was replaced with NAND4?


texts:
I have a problem with the CAN communication on a custom board with STM32F412.
The problem is that the CAN mailboxes run full and CAN communication comes to a halt.
This happend with the transceiver in Normal mode as well as in Loopback mode.
This is the code I use for sending:
if (HAL_CAN_GetTxMailboxesFreeLevel(CAN_HANDLE) > 0)
{
    HAL_StatusTypeDef retVal = HAL_CAN_AddTxMessage(CAN_HANDLE, &canMsg.header, canMsg.data, &canMailbox);

    switch (retVal) // used for counting errors
    {
    case HAL_OK:
        ++halOkHits; // counts up
        break;
    case HAL_ERROR:
        ++halErrorHits; // stays zero
        break;
    case HAL_BUSY:
        ++halBusyHits; // stays zero
        break;
    case HAL_TIMEOUT:
        ++halTimeoutHits; // stays zero
        break;
    }
}
else
{
    ++halAppMailboxFullCounter; // counts up; graph is shown below

    HAL_CAN_AbortTxRequest(CAN_HANDLE, CAN_TX_MAILBOX0);
}

The following graph shows the value of halAppMailboxFullCounter.

All messages are sent every second.
A connected PCAN-Adapter shows a bus load of ~30% with a peak at 37%.
For our case it's OK to drop some messages, that's why I clear the first mailbox in case none is free. This is done to free the mailboxes in case of an erratic bus.
The PriorityQueue feature of the CAN transceiver is turned off, so all messages should be treated equally.
Does anyone have an explanation for the fact the every ten seconds (the steps in the graph are ten seconds wide) the mailbox runs full for a few cycles?
Also, why does the occurrence of full mailboxes decrease over time? Has onyone seen this before?
Edit to address some issues Jeroen3 brought up:

The reason for only aborting one mailbox war to only skip the one message that might be stuck (no ACK on the bus) ... But this appoach has so many assumptions in it that I always wanted to investigate further ... It might not be the right thing to do. However, the graph looks the same if I abort all three mailboxes every time there is no free one.
The automatic retransmit feature is disabled.

Edit on new observations:

The same graph shows if the CAN transceiver is set to Loopback mode.

Solved one issue:
We solved the issue with the communication getting stuck by overhaulung the cabling. ... This does not change the full mailboxes drawing a stairs pattern ... I will go back to the stm32f4 reference manual and rethink our sending approach as Jeroen3 suggested.
Thanks for any pointers


texts: How do I increase the Ah rating of a battery?  Will connecting two batteries in parallel increase the overall AH rating?


texts: Can I describe this circuit as a highpass filter?

texts:
The input is square wave and the "filter" followed by two NOT gates. It's used to drive a bibolar transistor to reset an integrator(not shown).

I described this circuit to my professor as a highpass filter that responds only to the edges of the square input, followed by a buffer (2 not gate). I know that the gates convert the analog pulses to digital pulses but I don't know a suitable scientific name.

Anyway he told me that it's not a filter and the gates ain't a buffer (Actually he didn't even tell me what are they :D .)

Is that correct?


texts: I know that cache memory is much faster than typical RAMs. Apart from that, what exactly is the difference between Cache memory and shadow RAM? Both of them will have data that are to be accessed faster and frequently. In that case what goes into the shadow RAM area, and what goes into Cache?


texts:
Is it possible to multiplex multiple power LED strings from a single driver unit to reduce heat generated?

For example I have two 20 Watt (100V @ 200mA) LED lamps.

If I include an electronic switch between driver and lamps, and switch them at an interval of 5 secs. will there be any problem?


texts:
I am using Eagle5.11 to prepare schematic diagram. I need the .lbr file for

Breakaway-Male Header,CAT9532 SOIC 28 pin package..

So where can i find a bulk of .lbr files for these small but necessary components?

What other .lbr's you would suggest for a guy preparing schematics for his projects that includes things like interfacing pic mcu(16f/32mx) with driver ic's(uln2003) and lots of sensors?

I got one from sparkfun but that doesnt contain what I am looking for

Thanks in advance..


texts: Why does conventional electricity flow out of + in a battery, but out of - in components?

texts: It seems like when electricity flows out of + in a battery it should be attracted by a - end of a component, but it's not like that. Why?


texts:
My board will be mostly powered with an already regulated 5V input from USB (or wall charger), but I want it protected for higher supply voltage in case somebody plugs in the wrong voltage.

So I'm putting a voltage regulator on the board after Vin.

Initially I was planning to use the LP2985 but realised I may need to draw higher current, probably around 1A, so I'm considering the LM1117.

I see it is used on the Arduino Nano, which accepts 5V as an input, but after reading the datasheet, I understand Vin needs to be higher than Vout.

Can I use the LM1117 to convert 5V to 5V ?


texts: I am designing an isolated DC-DC converter with an input of 12V and an output of 5V@12A, at the moment, a flyback seems like the best option. I have read several books regarding the subject and I am proceeding to the implementation; however, I haven't been able to find a transformer that meets my requirements (I have searched on Mouser, Digikey and Newark to no avail). I suppose I've been searching incorrectly, since most of the transformers I have found can only manage up to 2A. I currently have no limitation regarding frequency or turns, but I would like to find the perfect match. So, where can I get the transformer I need? (Do have in mind that I require a website that can ship to Mexico)


texts:
I have a sinusoidal input signal (with a swing of 100mV roughly) centered around 100mV (DC). This signal needs to be input to a CMOS inverter. For this I need to level shift my signal around the inverter's threshold voltage.
I need a transistor level schematic that does just that: level shift my sinus input signal around the inverter's threshold, preferably with some form of feedback to deal with threshold voltage variations of the CMOS inverter (i.e. a circuit that shifts the signal around the inverter's threshold, even if that threshold voltage value changes).

Is this possible ?
Any ideas as to how this could be done ?


texts: Why are 3.8V lithium-ion batteries used in mobile devices, rather than 3.6V or 3.7V batteries?

texts:
I've noticed an odd trend in the lithium-ion batteries used in smartphones and tablets: rather than the 3.6V or 3.7V per cell typical of most Li-ion batteries in other types of consumer devices, they use 3.8V batteries that are charged to a maximum voltage of 4.35V (this is the case with both my Nexus 5X and Nexus 9). In at least one case (the LG G5 battery), the battery has a nominal voltage of 3.85V and is charged to 4.4V.

What's with these high-voltage Li-ion cells? I can understand that the higher voltage translates to more overall energy, but why pursue higher voltage instead of just higher capacity (as is done with 18650 cells)? Is there a drawback to using this type of battery?

A chat discussion starting here suggests that this higher voltage is specific to Li-poly batteries and does not apply to cylindrical cells like 18650 or prismatic cells like the sort used in compact camera batteries. Is this indeed the case?


texts: Does CodeWarrior IDE support software debugging of MCF51JM128?

texts:
IDE -CodeWarrior

Microcontroller-MCF51JM128


texts: ARM Cortex cores with peripherals, basic requirements

texts:
I've been reading a lot of stuff about using ARM tool chain to build applications for different microcontrollers including ARM cores. Right now, I've been using the fairly easy route with Atmel Studio 7 for xmega devices.

I understand that header files are provided by Atmel Studio 7 for their devices (in my case, the ATSAME70Q21.h or the XMEGA64A3U.h for past projects) which points to all the peripherals available in the microcontroller.

My question is, what is the bare minimum header files required if I have a ARM cortex based microcontroller with it's peripherals? Can I build directly with CMSIS? But as CMSIS seems to be only an API for standard ARM core processors, what happens with the peripherals (like UART, I2C,etc..), do I even need a header file definition for a particular device? If I build over CMSIS, does it mean I could easily port my project from say an Atmel ATSAM to an STM32?

I see these blocks but I don't quite understand how they piece together:

The ARM tool chain for compliling
Vendor specific header files for peripheral definitions.
CMSIS core
CMSIS implementations? Where are they?

And let's say a CMSIS implentation doesn't exist, how much am I screwed? Can I write this myself based on the datasheet, or is it just a waste of time?

Quite a lot of questions in this post. That show how much I am confused. I like using Atmel Studio, but I prefer when I can do projets from the bare metal and understand how the piece fit together instead of relying on magic code that could vanish in a future version of the IDE.


texts:
I was looking through 3.3V LDOs and I came across this

https://uk.rs-online.com/web/p/low-dropout-voltage-regulators/9115697/

It's a 3.3V LDO yet the minimum input voltage is 2.3V. How can that be possible?


texts: Best practices for parallel DC/DC Boost Converters

texts:
I'm working on a portable project that takes 4 (appropriately-rated) Li-Ion cells in a 4S configuration (14.46-16.8V) and boosts it to 27V for a 10-20 Ohm resistive load (soldering iron).  The majority of the purpose of the project is because I want the learning experience; I know there are commercial offerings.
Running my numbers, I'll be pumping ~70-80W around, which is higher power than anything I've done before.  I spent a good amount of time trying to find a DC/DC converter that could handle the amperage I needed, but ultimately came up short.  I DID, however, find an interesting example of a "2-phase converter" in the LT3579-1 documentation (side note: if I drop the out voltage a bit, that converter could handle the load at just about it's absolutely maximum rating... so I have a fallback).
This 2-phase converter had the FB pins and the Error Amplifier Output (VComp) pins of 2 ICs tied together, and the ICs were also synchronized (well, actually un-synchronized, 180 degrees out-of-phase) by way of some included circuitry.  That chip is more than I want to spend, but it got me wondering if the approach would work generally for a step-up converter:

Build N (or maybe N+1 to be safe) identical DC/DC Step-Up circuits on the board
Tie all the FB lines together, as well as all the VComp lines
Since the outputs on the DC/DC regulators are already going through a diode, I don't need to worry about the current from one flowing back into another
Generate a frequency/clock that is (N or N+1) times as high as the IC's spec, then put it through an (N or N+1) divider to clock each IC as out-of-phase with the others as possible.

Is this a reasonable approach?  I figure I'll get better efficiency at lower (not TOO low) current, too - so less total heat, plus I'll be dividing the heat that is generated across multiple chips, so it should be easier to manage all around.  Am I missing something?  Is this a good approach?  Are there things I should watch out for - specific regulators that won't work in this configuration, etc?  Thank you!


texts: Amplify Raspberry Pi Zero W Audio with 60s Tube amplifier circuit

texts:
First of all, thank you for taking a look at my question.
Electronics is not my field of expertise, and I have found myself a bit stuck.

I have been restoring some old 50s and 60s tube amplified radios, fitting them with Bluetooth while maintaining the original electronics and functionalities. I achieved this by connecting the Bluetooth audio to the record player input of the radio. This worked relatively okay.

Now I am thinking of making a radio into a smart speaker, using a Raspberry Pi zero W and the open source google assistant software and connect this to the radio.

This is where my problem lies. As the raspberry pi zero does not have any audio output except for over HDMI, I will need some sort of circuit.
From the research I have done it seems the way audio works on the pi is using the PWM pins. There are some boards online, like the PAM8403 as well as pHAT DACs. However, it is unclear to me if this work as I intend, as they are all meant to be the final amplifier and directly drive the speakers, not be amplified again through for example my tube amplifier system in the old radios.

The points of confusion originate from the following:
- PWM can be used for the audio, I am confused if this is then used as I2C, i.e. digital which has to be converted to analog, or is this PWM used to create an analog signal? If so, then I might be able to directly pass it into the radio?
- The PAM8403 board is a class D (digital) amplifier. I have read on sources that connecting together the L- and R- could cause problems, but to connect it to the radio I have a L, R and common ground.
- The PAM8403 is 3W output, the radio however I think is used to a very low powered input signal from the record player, would this not blow up the entire radio? Could I just fix this by using a simple voltage divider?

I guess what it comes down to is that I need a low power analog signal from my Raspberry Pi? I have found things like HifiBerry, but I am looking for a more budget friendly solution as I believe those are a bit of an overkill. I would prefer a ready made solution that I can buy but am also open to making my own if it is not too complicated.

Thank you for taking the time to read my question, if there is any more information please do not hesitate to ask.


texts: How to design DC Motor speed control, using PID

texts: I am looking to control the speed of a DC Motor using PID, it is speed control. I understand how the PID works, but i have a few questions. Like,how would I find my gains for each of the PID, what values of resistors and caps would I use? Also, would a simple 5V DC motor be suffice? If anyone has done something like this, a circuit schematic would be great. Thanks


texts:
I calculated the breakaway points. They come out to be

Root 1: -2.481
Root 2: -0.689
Root 3: 1.17

because of root locus properties only the -2.481 will fall on root locus . But when I saw the solution there were no going towards breakaway points. I just want to know when to calculate the breakaway points.


texts:
Let's consider the slide 1 of this material.

I have understood the computation of S11, but not that of S21.

I do not understand:
- why there is the circuit with V and two impedances Z0 and there is not Zx. What does this circuit represent?

Why then it considers the circuit with also Zx.
Why the source is added together with an output impedance (Z0): I have seen examples of computation of S parameters by adding only an ideal voltage source, without output impedance.


texts: What logic family does NXP 1114 MCU belongs to?

texts:
Title itself is explanatory. Also tell me what are the things I should take care of when I connect other IC's to it? With AVR's I never had to deal with these things. But now when dealing with ARM MCU's I think I have to consider these stuffs.

I will rephrase the question. Tell me, is it safe to connect LPC MCU to other common IC's like an AVR or L293D diver IC or 74xx series IC's etc without any interfacing circuits?


texts:
Like the title says, I was trying to bootstrap a high-side NMOS. After some googling I found this video https://youtu.be/zcQV_ZpK1W8 which helped me a lot except for one thing which I cannot understand.

Now, my proposed circuit is this
It is pretty much similar to his but with the capacitor connected directly to ground.

When the NPN transistor is ON, the capacitor charges up to Vcc, which is the same for my and his circuit (I think). The problem is when it is OFF, when the load should be ON. What I previously thought was that the capacitor “pushes” Vcc into the MOSFET’s gate, and so does the battery (or whatever voltage source we’re using) through the diode to the gate. Thus, we have 2Vcc at the gate. I now see that this is wrong because my circuit has it as if the battery and the capacitor were connected in parallel, which will NOT give the sum of the emfs.

However, I can’t see why his circuit works. He says at the end of the video that since the load has 12V across it and so does the capacitor which is in series with it, then the end result is that the gate has 24V. How does electricity work “backwards”? If “potential” is basically the energy per unit charge, how does the energy flow backwards from the load to the capacitor to the gate? I am just not convinced. What am I missing?

Thanks in advance!


texts:
I'm running a Hello World that toggles RB7:

#include <p16f1509.inc>
    __config _CONFIG1, _FOSC_INTOSC

    udata
delay0  res 1
delay1  res 1
delay2  res 1
delay3  res 1
ledState res 1

delay32 macro delay
    goto $+1
    goto $+1

    banksel delay3

    movlw   (delay - 1) & 0xFF
    movwf   delay0

    movlw   (delay - 1) >> 0x08 & 0xFF
    movwf   delay1

    movlw   (delay - 1) >> 0x10 & 0xFF
    movwf   delay2

    movlw   (delay - 1) >> 0x18 & 0xFF
    movwf   delay3

    call    doDelay32
    endm

rst code 0x00

start:
    clrf    PORTB
    banksel TRISB
    clrf    TRISB

    banksel ANSELB
    clrf    ANSELB

    movlw   0x80
    movwf   PORTB

    banksel ledState
    movlw   0x00
    movwf   ledState

loop:
    banksel ledState
    movf   ledState, 0
    xorlw   0x80
    movwf   ledState
    movwf   PORTB

    delay32 d'2500'

    goto loop

doDelay32
    movlw   0xFF

    addwf   delay0, F
    btfsc   STATUS, C
    clrw

    addwf   delay1, F
    btfsc   STATUS, C
    clrw

    addwf   delay2, F
    btfsc   STATUS, C
    clrw

    addwf   delay3, F
    btfsc   STATUS, C
    clrw

    iorwf   delay0, W
    iorwf   delay1, W
    iorwf   delay2, W
    iorwf   delay3, W

    btfss   STATUS, Z
    goto    doDelay32
    retlw   0

 end

This runs perfectly on the MPLABX debugger using a PicKit3, but does not run otherwise.

This appears to be a common problem, but a day of Googling has turned up nothing useful. Here's what I've learned:

Most people fail to pull MCLR high. I have a 10k between MCLR and VDD.
The clock config bit defaults to an exteral clock. Setting it to INTOSC didn't help.
Some people suggest setting the !DEBUG bit, but the data sheet claims that this is totally taken care of by the debugger. I tried it anyway; it didn't help.

Any suggestions would be appreciated.
Thanks

Also: Does anybody know if it's possible to program a PIC using a Beaglebone's by connecting I2C to ICSPDAT and ICSPCLK?


texts: How to connect AFC terminal on Crystal Oscillator

texts:
I'm thinking of using a Temperature compensated crystal oscillator in my next project, specifically the TXC 7L-38.400MBS-T

This device has an AFC (Automatic Frequency Control) terminal, but no advice is given in the datasheet about how to connect this, and I can't find any information anywhere else on the web or on any other datasheets for other TXCOs.

What should I do with the AFC terminal? Leave it floating? Ground it?


texts:
My Wifi router claims to provide bit rate upto 300Mbps and support 802.11 b/g/n. But 802.11n standard requires using 4 streams(4x4 MIMO technique) using 4 different antennas. Mine has only 2 antennas. It should have been capable of providing only 2x72 Mbps(54Mbps x 4/3 (taken from 802.11g) times the number of antennas).
How is my router claiming to provide a speed that can only be achieved using 4 antennas while it has only 2 antennas.
(I am under the assumption that each antenna caters to adding 1 spatial path)


texts: Arduino + Max7221 + Common anode 4-digit 7-seg LED array?

texts:
I'm trying to hookup a common anode 4-digit 7-segment LED array to my Arduino via a Max7221 IC.

Here's a hard-to-see (sorry!) pinout for my LED array (my LED array is the bottom common anode one, LFC0566XXX)

Here's the datasheet for the Max7221 IC that I'm using.

I was following a tutorial on the Arduino Wiki and it said that the Max7221 will not work with common anode LED arrays like the one I have. However, the comments on the Max7221 Sparkfun product page say that it is possible to use it:

  You can drive common anode displays with this chip just fine. It has 8
  cathode outputs and 8 anode outputs. The only thing you lose is the
  BCD-7 segment decoder, which would work strangely hooked up to a
  common anode 7 segment display. But if you’re just telling the chip
  which segments to light directly, it’ll work just fine either way.

How can I connect my LED array to the Max7221?


texts: How to generate 1min timer interrupt in PIC24F

texts:
I m trying to generate a 1 minute interrupt using
pic24F seires... To be specific PIC24Fj64GA306

Here is the code snippet

#include "xc.h"
#include "newxc16_header.h"

void TimerInit(void);
void __attribute__((__interrupt__)) _T1Interrupt(void);

void main()
{
    ANSB = 0x0000;
    TRISBbits.TRISB0 = 0;
   TRISBbits.TRISB1 = 1;
    TRISBbits.TRISB2 = 1;
   TRISBbits.TRISB3 = 1;
    TRISBbits.TRISB4 = 1;
    TRISBbits.TRISB5 = 1;
    TRISBbits.TRISB6 = 1;
   TRISBbits.TRISB7 = 1;
   TRISBbits.TRISB8 = 1;
   TRISBbits.TRISB9 = 1;
   TRISBbits.TRISB10 = 1;
   TRISBbits.TRISB11 = 1;
   TRISBbits.TRISB12 = 1;
   TRISBbits.TRISB13 = 1;
   TRISBbits.TRISB14 = 1;
   TRISBbits.TRISB15 = 1;

   TimerInit();

   T1CONbits.TON = 1; //start the timer

   while(1)
   {

   }
 }

void TimerInit(void)
{
  PR1 = 0x1FFF;  //8191
  IPC0bits.T1IP = 5;     //set interrupt priority
  T1CONbits.TCKPS = 0x03; //timer prescaler bits
  T1CONbits.TCS = 0;   //using FOSC/2

  IFS0bits.T1IF = 0;    //reset interrupt flag
  IEC0bits.T1IE = 1;     //turn on the timer1 interrupt

}

  void __attribute__((__interrupt__, auto_psv)) _T1Interrupt(void)
   {
     T1CONbits.TON = 0;   //stop the timer
     LATBbits.LATB0 = ~LATBbits.LATB0;  //Toggle output to LED
    IFS0bits.T1IF = 0;   //reset the interrupt flag
     T1CONbits.TON = 1;   //start timer
  }

For testing purpose i m trying to generate Timer interrupt after every 1 sec...

But the issue is i m not able to generate any interrupt.

Please help me.

Thanks in advance


texts: Directly Power STM32 from Lithium Battery

texts:
I'm putting together a wireless sensor node and it's running a STM32L051 which can run at a 1.65-3.6v range. I've also got an RFM69HW radio onboard which can run at 1.8-3.6 (2.4-3.6 for full power output)and will draw at most 130mA.

I'm looking to see if I can power this straight from the battery, an NCR18650B Lithium Ion. The trouble I'm seeing is that while everywhere states these are 3.6v nominal, the graphs often start at over 4v. Is this just when the battery is not loaded?

Can I just stick an IN5819 diode in series with the battery to get a ~.6v drop and have a range of 3.6-.6=3.0v (4.2-.6=3.6v??) to 3.0-.6=2.4v. If I do, does a bigger forward voltage mean more power loss, resulting in less runtime? If that's the case, maybe I could get away with a Schottky diode that has a smaller voltage drop if the LiPo really is at 3.6v and lose less power?

The goal is the longest runtime.


texts: I am using analogWrite(PWM) from Arduino UNO to control the gates of 30N06L N-channel mosfets. The values of PWM are programmed such that it controls the current through the loads for my control design. I am printing PWM (as controller's output) every second. Are these printed PWM values averaged one or not? Is it OK to write PWM values(doing some math) as the voltage instead of writing it as duty cycle? The frequency of signals from analogWrite(PWM) pin is 490Hz, which makes the time period of pulse to be about 2 ms. Thus I assume we can take those PWM printed every seconds as averaged one.Furthermore I could not find any information about the frequency response (regarding PWM) from 30N06L N-channel mosfets datasheets? Any suggestions will be greatly appreciated.


texts: Downside of using superspeed pairs as USB 2.0

texts:
For time/cost saving reasons, I want to use a USB 3 cable as a USB 2 cable. The cable will be carrying other (slow) signals, and so extra conductors are needed (which is why I can't just use a usb 2.0 cable). I know that the USB 3 cable has a differential pair meant for USB 2 signals, but for improved shielding, I want to use one of the (shielded) Superspeed pairs for the USB 2 instead. Are there any downsides to this? From what I can tell, the impedance of all the twisted pairs are 90 Ohms.

I'm making the devices on both ends, and they'll have custom connectors, so compatibility with other stuff isn't important. To be clear, the custom connectors are not USB connectors.


texts: Why is the datasheet showing VGS at absolute maximum?

texts:
I'm looking at IRLZ44N datasheet.
In the ABSOLUTE MAXIMUM section it is listed that for VGS it is 5V. However in the SPECIFICATIONS section below VGS threshold is listed as 1V to 2V.
At the same time in the ABSOLUTE MAXIMUM section the continuous drain current is given as 36A to 50A at 5V VGS.
Isn't the absolute maximum a value that you should normally stay away from to prolong the component's lifetime? I understand that this is in the absolute maximums section which is probably why they put such test conditions to achieve maximum results but if you go down to the SPECIFICATIONS section you'll see that RDSon is also given at 5V and 4V VGS.
Excuse my ignorance but this is slightly confusing to me. If my assumption is correct that you should stay away from the 5V VGS then how can I calculate the expected RDSon at 1V to 2V?


texts:
I just started to learn the sequential logic and I am a little bit confused of the difference between the latch and flipflop. More specifically, I am confused about the difference between edge triggered and level triggered.

So, I learned master slave flip flop first other than other flip flop. Then, I understood pretty well why master slave flip flop is edge triggered. I think it is the NOT gate of the clock signal to the second component that makes it edge triggered.(Not sure whether that second or first component is D flip-flop or D latch either)

However, then I came to learn about this SR flip-flop and even D flip-flop. And suddenly, I got confused about the difference between edge triggered and level triggered.

How is this SR flipflop edge triggered? Shouldn't it be level triggered since as long as the clock signal is HIGH, everytime the input changes, the output will respond to it.

I think flip-flop is always edge-triggered? Am I misunderstanding something?


texts: Controlling a motor from Android device for small dumbwaiter

texts:
In short, I am trying to build a motorized dumbwaiter (platform to carry small objects up and down vertically) from the ground to my office, which is about 15 feet higher than ground level. I would like to be able to control the dumbwaiter (move it from the ground level up to the office and vice versa) via an Android phone.

I realize this isn't the most practical method to get small objects, like a cup of coffee, from the ground floor to my office, but it should be a fun project and good way to learn about Android development and related technologies, likely Bluetooth.

What would be the best way for the dumbwaiter motor to 'talk' to an Android device? I'm familiar with Bluetooth, but open to other suggestions as well. Also, any suggestions on types of motors that can be configured to respond to Bluetooth out of the box or with minimal tinkering?

Sorry it's such a broad question, and my first on Stackoverflow, but any help is really appreciated.


texts: I need schematic of this simple microphone

texts:
wires inside the  microphone were cut and I don't know the correct place of wires to solder them so I need schematic  or your explanation to repair this microphone.

This microphone contains only four items;  switch, 2.2kohm resistor, microphone capsule and 1.5v battery.
The microphone has three cut wires:two of these wires connected to jack. and third wire is connected to negative terminal of 1.5 v battery and positive terminal of battery connects to microphone capsule.And another side of microphone capsule connected to microphone body.

The  switch of the microphone has three pins and one side of a 2.2 kohm resistor connected to center pin of switch and other side of resistor connected to body of switch.A side pin of switch doesn't have any solder,it seems any wire weren't connected to this pin.
image of microphone


texts: strange RFM95 SPI behaviour with STM32L4

texts:
I am using CubeMX and HAL to program an STM32L4. I am trying to communicate with RFM96 module using SPI, but I am getting nonsensical results.

According to the RFM96 datasheet, in order to read a byte from an address, I have to send 1 byte, MSB set to 0 (indicating read mode), the other 7 bits indicate the address. In the screenshot below you will see I am attempting to read the value of register 0x03, which is supposed to return value 0x0B (default). The problem is that instead of receiving only 0x0B, I receive what looks like ALL the register values of RFM95. You will see that 0x0B is present too.

I have let the clock go on for 8 bytes more than I need to, just to demonstrate the issue. Furthermore, I only experience this result if the LSB of the first byte is 1. If I request the data at address 0x02, I would get zero response (picture below). I get the same response if I send 0x00.

This is the code I use to generate the above logic analyser samples.

uint8_t data[10];
data[0] = 0b00000011;//sent first
data[1] = 0b00000000;
data[2] = 0b00000000;
data[3] = 0b00000000;
data[4] = 0b00000000;
data[5] = 0b00000000;
data[6] = 0b00000000;
data[7] = 0b00000000;
data[8] = 0b00000000;
data[9] = 0b00000000;

HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_RESET);
HAL_SPI_Receive(&hspi1, (uint8_t *)data, 10, 100);
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET);

This is my SPI init function:

  hspi1.Instance = SPI1;
  hspi1.Init.Mode = SPI_MODE_MASTER;
  hspi1.Init.Direction = SPI_DIRECTION_2LINES;
  hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi1.Init.NSS = SPI_NSS_SOFT;
  hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
  hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi1.Init.CRCPolynomial = 7;
  hspi1.Init.CRCLength = SPI_CRC_LENGTH_DATASIZE;
  hspi1.Init.NSSPMode = SPI_NSS_PULSE_ENABLE;

This code is rudimentary; I am using a logic analyser to debug. Can anyone spot what I am doing wrong? As far as I can tell, I am giving the RFM95 all the requirements it needs in terms of MOSI, SCK, and NSS.


texts: In which physical unit is 'clock drift' measured?

texts:
I would like to model a clock signal with an drift parameter in my digital simulation.

The current implementation handles:

frequency / period
phase -360.0 .. 360.0 degree
duty cycle 0.0 .. 1.0

Unimplemented properties:

drift
jitter

For clock domain crossing circuits, I would like to implement a primary (stable) and secondary (drifting) clock. I know that my digital model can not handle metastabiliy problems -- that not my goal at all -- but I could detect handshake errors.

*Clock drift is not jitter. Clocks running at the same speed may varie in sub percent ranges, so one circuit is running a bit faster.*

Most documents have only ratings for jitter, on the other hand transceivers, like in FPGAs, have phase compensation units which do phase correction automatically. I can't find a max value for them ...

So my questions are:
  - Is it an absolut or relative value?
  - If relative, relative to what: one cycle, 1 second, ...?

If someone has suggestion on how to model jitter, it will be welcome too :).


texts:
I have LT1086 5V regulator

what is the Vin min to provide 5V output?( assume load current 500mA -800mA)

I tested it worked for 6V Vin,

but datasheet does not mention anything about Vin min

https://www.analog.com/media/en/technical-documentation/data-sheets/1086ffs.pdf


texts:
Background:
I am trying to make a push pull dc-dc converter from 12vdc to 400vdc for an inverter with a center tapped transformer connected to battery of 12vdc. The MOSFET circuit is as follows

As can be seen in the figure, there is severe ringing in the drain waveform of the two MOSFETS. The upper blue waveshape is the drain wave, while the yellow is the gate waveform.
What could be the cause, and what could I do to get a clean wave shape on the drains.

I have added a non-dissipative clamp, like so

Then I got these wave shapes, on both sides, with blue being the gate signal:

Now my question is, If I add a passive RCD snubber between the drain and source of the mOSFETs, will that be sufficient to get a good 'square' wave shape on the secondary??


texts: Help me to understand the simplest voltage multiplers

texts:
I attached a picture of the Villard circuit bellow. I can't seem to understand why the capacitor stays charged-up. Since I = CdV/dt, a capacitor finishes being charged at the crests of the voltage sine wave. A capacitor alone would then begin uncharging (see the second picture). The thing that is confusing me is that for the Villard, after the peak voltage, the voltage is obviously still positive (since the voltage and current are 90 degrees out of phase). Wouldn't this mean that the diode is forward-biased? Isn't it supposed to act like a plain conductor when it is forward-biased? If so then why doesn't the capacitor just discharge through it? BTW with the voltage and current 90 degrees out of phase, the current can flow in both directions when the voltage is above zero, right? (One direction while voltage is rising, the other while it is falling).

Perhaps the explanation is that a diode only lets current flow in one direction, if it is forward biased too.

Obviously this goes toward understanding the fundamentals. Feel free to throw what you like at me.

Villard Circuit

AC Voltage source and capacitor


texts: Gain and offset adjustment with voltage reference?

texts:
I am building an instrument that relies on a precision sensor module. The sensor is factory-calibrated, and outputs 0-10Vdc. I believe the factory calibration to be better than anything I can attain, and thus do not want to create my own calibration curve for the sensor.

I want to read this output with a 16-bit ADC; however, most ADCs only accept 0-3Vdc input. I will likely need an offset/gain op amp circuit between the ADC and the sensor, but I want this to be referenced to a known voltage reference. For example, I also want to run a known precision voltage reference through the offset/gain circuit to known that a given reading from the ADC corresponds exactly to a given reading on the sensor independent of temperature and everything else that could affect the reading. I want to be sure that I can determine the exact voltage coming off the sensor.

Can someone provide a schematic for such a circuit? Or at least point me to such a resource.

Thank you,

Michael

EDIT:

A number of commenters have asked about the specifics of my application (sorry! it took me a bit to dig up the datasheet). I am interfacing with an INFICON Priani Capacitance Diaphragm Gauge (a vacuum sensor). The device has a signal output with an absolute maximum range of 0-10Vdc; however actual measurements stay within the 2.2-8.68Vdc range. The accuracy of the voltage output is not stated because the device operates on a logarithmic scale. Voltage is directly proportional to the logarithm of pressure. The data sheet states the pressure measurement (not voltage) is ±15% accurate at 50 mbar, ±5% at 1000 mbar, and ±2% accurate at atmospheric pressure. The conversion factor is P = 10^(U-5.5) where P is pressure in mbar, and U is voltage.

The logarithmic output of the sensor is why I am concerned about accuracy (not so much precision). Errors in voltage measurement are amplified exponentially by the logarithmic nature of the device.

Vacuum Gauge User Manual Inficon PCG410


texts:
I am building a circuit that amplifies an electret microphone with the use of an op amp. It does work, but I am getting a lot of noise at the output side of the op amp when I connect it to a pair of headphones (indicated by the speaker.)

simulate this circuit – Schematic created using CircuitLab
What could be the cause of this?
Edit: I am using an Arduino +5V as power supply (which is powered via USB.)


texts:
The datasheet says the MCP2561/MCP2562 is suitable for 12V and 24V systems except that everywhere I look in the datasheet it says VDD needs to be between 4.5 to 5V. How can CANH be greater than VDD or CANL be lower than VSS?? How would these internal MOSFETs work (shown on page 2 of datasheet) ?

Looking at CANH and CANL also got me wondering what are CANH and CANL referenced to? For example if I want to have a 12V CANbus, how do I get those lines to 12V - how are they pulled up/down?


texts: How far away can I place the dropping resistor from a diode?

texts: I plan to desolder the infrared diode from my raspberry-pi to add a 30cm long wire to it and solder it again. Do I need to solder the pre resistor right next to the infrared diode?


texts: Which files to version control for KiCAD?

texts:
I'm trying to create the .gitignore file for a KiCAD project that is versioned with git and stored remotely on GitHub.

What are the minimum files I should I add to my version control system in order for others to replicate the project?


texts: In configuration B in the image below, what do the triangles mean?


texts: Startup voltage help: How can I change the input voltage to this IC when starting the circuit?

texts:
I am currently trying to find a solution to switching the supply voltage for U12 (PN: UC3842BVD1R2G) in the included schematic. What is special here is that U12 will draw 22mA no matter the input voltage I tested at, I did a sweep from 13v to 30v and it always only pulled 23mA. The issue here, is that even though it can be supplied with 30v, running it off the usual 24v causes the chip to run at 170 F, which in my case is a problem, and is near the high end of the recommended temps. Running the chip at 15v however, causes it to run at about 120 F, much better. The other issue with just trying to connect a 15v regulator right away is that the chip needs over 16v to start the circuit, then can be brought back down to 12-15v and run off of that.
I am attempting to start u12 on the input voltage, then when the regulator starts up, to use that to turn off Q1, changing the input from the 24v line to the 15v line. However, I don't think that would work, and was wondering if there is a normally closed held open kind of device that could do something like this? I also don't have a lot of space on this board for some type of relay either, or that would have been first choice.
Any help appreciated.


texts: Altium: escape from "Top layer (flipped)" view

texts: While I was using Altium Designer 19, I somehow managed to mirror the PCB across the Y axis, so now I am in view mode "Top layer (flipped)". How can I get back to normal view?


texts: Unusual chemical reaction on PCB (SMPS circuit)

texts:
I have a PCB with smps circuit on it 220V to 5V (using Viper22a). Here is the schematic:

And here is the board layout:

In the yellow circle region, I am seeing some sort of white deposition in a few PCBs(bottom layer). Please see the images below:

Once scraped off, it takes away the solder mask with it. Deposition starts on both auxiliary winding pins and extends to the diode (bottom layer). Remaining area seems to be unaffected. What could be the reason behind it and how do I avoid such a thing?

I think some sort of chemical reaction is going on probably due to cheap materials used during fabrication or maybe due to improper cleaning of solder flux after soldering. But again, primary winding should be having a higher voltage and hence a better spot for such chemical reactions.

I don't see a temperature rise in that area. It feels cold to the touch.

Updates: I had a feeling that this is some sort of chemical reaction. I immediately checked the place where I had placed the PCBs and I found these:

I placed the bare powered PCB on marble thinking it to be insulating. Seems like acid traces from the flux initiated ionic disintegration in the marble first and then DC current pushed the reaction even further. White deposit is deposited calcium it seems. As seen from the marble image, it seems corroded. On touch, it feels rough as if someone dropped a drop of acid on it.


texts: I have found a 3 pinned IC with part no S3008 on my Defy automatic washing machine control that needs to be replaced. Is it a Transistor? If it is, is it PNP or NPN?


texts:
https://www.tinkercad.com/things/2CN1eOTbmTe

I am a beginner in electronics.

I've been trying to make an astable 555 Timer in TinkerCAD as an oscillator for my own project of making a clock, without using internal timers in Arduino ( I know it's pointless, but it's a challenge I set for myself to learn more ). No matter what I've tried, the circuit gets stuck on high or if arranged in another manner, low and the capacitor doesn't seem to be doing anything, based on the serial log outputs.

I've compared it to existing schematics and it all seems correct to me. Help would be very much appreciated.

EDIT: I've trimmed the circuit down to the bare minimum to make it easier to understand..


texts: Calculating chip junction temperature based on case temperature

texts:
As far as I know one can calculate a  chip’s (Diode, Transistor..) junction temperature rise with the consumed power and the thermal resistance Rth.
Is there a way to calculate the junction temperature without the power but based on the temperature measured on the Chip‘s case and Rth or other datasheet values?
The reason for this question is my desire to check the temperature handling on an existing PCB without changing it by my measurements (for example soldering some parts up for current measurments).


texts: Creating a powered USB hub, trying to drop my voltage from 12v to 5v (AC/DC converter I have outputs 12v)

texts:
I'm trying to build a powered USB hub without buying additional parts.  So finding old electronics lying around the house kinda deal.

Anyways I have a 4 USB hub that I took apart to find the PCB was designed to accept an external power source (it has a jack silk screen and a capacitor silkscreen).  Good news!

I only was able to find this AC/DC converter however.  It outputs 12V and 1700mA.  USB devices are built for a Vcc of 5V, usually from 4.8V to 5.3V or so, and amperage varies though I've mostly seen 1A as the top value.

What are my options?  I'd love to build a circuit but I'm not very good with Electrical Engineering, and I only have Transistors (PNP and NPN), Capacitors, Resistors and a 595 timing chip to work with.

I should add I have a car inverter that I don't use, one with a USB port on it.  Is it viable to take that apart?  I'm guessing it doesn't invert from 12v DC to 120V AC then back to 12V DC then drop it down to 5V, it probably just drops the DC to 5V.

Any advice welcome, I'm still very new to circuitry.


texts:
I am using this module: https://www.adafruit.com/product/1374

My idea is to sense a person wearing this module and when touched by another person, the LED lights up. I read numerous articles and Googled around and have a little understanding of how this could work.

The module works such that when it is powered it gets a "zero state" then when the touch pad is touched it turns the LED on, when my hand is on the sensor (since I will be wearing the touch sensor) this is recognized as the zero state.  When I touch another person, the LED lights (but only if I ground the circuit to earth – does not work when no external ground is provided).  I suspect that without earth ground, the capacitance difference between the two people is too minimal to be recognized.

So my question is, if there is a way to alter the circuit to recognize the difference of capacitance between two people? Either through an "artificial earth" or through some added component such as capacitor.  The idea is to be portable and wearable.


texts:
There are some parts that use the same part number across different vendors.
e.g.:

23cxx: SPI SRAM (only Microchip?)
24cxx: I2C EEPROM
25cxx: SPI EEPROM
27cxx: parallel EPROM (UV light erease)
28cxx: parallel EEPROM

and so on.
Is there a list of all the devices in that naming convention like for 74xx series ICs?


texts: What component allows DIP to be connected with Dupont style jumper wires?

texts:
(sorry for the n00b/cringey question!) I've order an ADC chip and I realized upon receiving it that standard Dupont style jumper wires don't fit on standard integrated chips pins.  I was wondering if an IC to jumper wire connector/socket even exists and if so, then what it's called.

Basically, what I'm aiming for is a single component that combines a DIP socket (at least 2x8 pins) and Dupont style jump wire header pins so that I can push my IC in that socket and connect jumper wires without any soldering.

The closest I could find is this guy who made himself a couple ones with breadboard, but does that exist as a single standard component?

Thx


texts: Can ANY DC brushless motor be used as a generator?

texts:
Question is pretty much in the title. I know it's definitely possible to use certain DC brushless motor as a generator, but is it always the case?

Thanks a lot in advance.


texts: KiCad -- layout, how to remove extra vertexes from filled zones

texts: In KiCad's layout tool, we can add a vertex to the outline of a "filled zone" with the "Insert" key. Sometimes I put in too many, change my mind etc, and they get annoying. How to remove them?


texts: How to control this system by using a single Opamp circuit?

texts:
Below is part of a circuit where an op-amp is creating a 10sec delay by C1 and R4:

(please left-click to enlarge)

The goal is that:
One will push one of the  push-button (one of the Myswitch in the schematic) and the magnet-group(R1 L1 which represents four electromagnets in series)
will get magnetized for 10 seconds and after 10 seconds the op-amp output will go off and the Q1 will be off hence the magnet will be off.
LED will be ON untill the electromagnet current is off so one can repeat the experiment when the LED is OFF.

But I need to make twenty of these circuits to control them separately so there will be twenty switches as follows(I could only draw 3 here):

My question is:

1-) Could there be way to use only one op-amp circuit and twenty switch instead?
In that case is it possible that when one of the button is pushed(lets say push button N is pushed) only one of the magnet-group(group N) will get powered?

2-) Is  R11, R8 values good for LM324 and TIP120? In simulation LM324 sources around 25mA. I chose LM324 in this case, would it be better to chose a 555 timer? Precision is not so critical, the delay could be 9 seconds upto 12 seconds.


texts:
I use the ENC28J60 MAC+PHY ethernet controller (datasheet) in a fairly standard setup as shown in the schematics below.

I can talk to the ENC via SPI, but I cannot get a link-up when I plug in an ethernet cable.
I am looking for suggestions how to narrow the error down.

My considerations so far:

I checked all electrical connections and they seem ok.
The MagJack is of this type. I have used a different one (this one) on a different, but working ENC setup. As I have not used this MagJack type before, it raises my suspicions. However the datasheet looks ok for me.
The crystal is of this type. The ENC datasheet says it requires the use of a "parallel cut" crystal. I am not sure if my crystal fulfills this requirement.
I use hand-soldered 0201 size load capacitors. Crazy, I know. The solder joints look ok. But as I cannot test them and they are so small, I suspect them as well.

I am not sure if the fact that I can talk to the ENC via SPI means that the crystal and the load caps work ok. If yes, then the MagJack would be my prime suspect.

So my next steps would be 1. replace the MagJack, if that fails, 2. replace crystal and load caps.

Any suggestions on more probable error causes, or ideas how to narrow the error down would help me greatly.

The schematics:

Notes on the schematics:

VCC is +3.3V.
I connected LEDs for LED A and B tied to GND, not shown in the schematics.


texts: Barrier and slot within reduced area on a PCB

texts:
Imagine this situation in a little area of your PCB:

According to the worst case and used material, I need a creepage distance = 30mm. According some tables, clearance must be 30mm. First Red banana and black connector will have the same voltage: HV. They will be connected by wire. But the next red banana could be at different voltage from black connector, being LV. Difference between black connector and the right red banana could arrive to 6 KV.

As the available PCB space is little I saw 2 solutions:

The cheapest and easiest way is to the make a slot on the green area. I will obtain desired creepage distance making the slot larger. But the problem is that clearance will surelly have a shorter distance than 3cm. Making the slot larger doesn't have any effect on clearence.
to put a barrier on the green area in order to increase creepage and clearance and achieve 3cm for both distances. But this kind of solution is expensive, especially if there are more than one barrier to fit.

My questions:

So, despite creepage has the priority I guess I will ensure the clearance will be achieved too, does it? So slot could not work here. Would you put a barrier or a slot?
If slot, any especial way to follow for drawing the slot shape?
What is the slot width? is it any way for calculating the hole width? I have read that 1mm could be de minimal slot width. But is ever a width = 1mm for enought?


texts: Atmega 328 with DS1620 thermometer chip. Why is a pull-up resistor needed on the DQ line

texts:
I think understand the purpose of pull up resistors in general but in this particular case the DS1620 datasheet says that in the output mode it sources a current of 1ma (see footnote 5 on the last page).
My understanding was that I would need a pull up resistor on the Atmega's input if the other side didn't source any current in the logical 1 state (high impedance), but in this case it says it sources current, why would I still need a pull up resistor enabled on the Atmega's input pin? (it doesn't work without the pull-up)


texts: Switching op-amp gain resistances - how?

texts:
Given the following circuit:

What is the component / circuit I should be using to switch the signal between each of the gain resistors?  (the ⊠s in the schematic)

The inputs ID0 to ID2 are TTL (could be active high or active low, I don't mind).  The input IA0 is analog \$\pm 2.5V\$, offset by \$+2.5V\$ by the voltage divider into the Op-Amp's non-inverting input.  The output OA0 is the same (offset).

The feedback therefore is obviously going to swing around the virtual ground \$0V\$ (not sure what that would equate to in this circuit) in both directions, so needs to handle that.

I don't want the switching mechanism to give any amplification, and preferably have as little \$R_{ON}\$ as possible.

I don't have a clue what I should be using to do this switching.  If it makes it easier I could fix the gain resistor to a known value and move the switching to the inverting input resistance (not shown on schematic).


texts: I want to make a circuit to indicate an LED if a motor is drawing too much current. (when the motor is stopped for example mud got stuck around the gears) I am using 9-12 volts to power my motor, and it seems to be drawing 100 milliamps running without a load. I Want the LED to indicate if it is drawing over 200 milliamps. How would i do this?


texts: Why does copper pour cause impedance discontinuities?

texts:
Inspired by this question's accepted answer, I've been studying how PCB trace impedance can be affected by the trace's surroundings. However, something in the accepted answer is confusing me:

  Having copper pour all over the place close to my signals!!! That would cause impedance discontinuities everywhere.

Why does this cause impedance discontinuities?

As I understand it, copper pour near a trace on the same layer causes an impedance discontinuity because it offers an capacitively coupled path as it runs adjacent to a signal trace. The coupling changes the capacitance for adjacent regions of the signal trace but not the remaining portion. This coupling occurs even if the copper pour is electrically isolated (for reasons I don't understand, but that is a separate question).

Is the above paragraph accurate? If so, are there other reasons for the impedance discontinuity?


texts: I have some trouble to design castellated cut outs for a pad, at least there is always thin copper area you can see in the pictures below. How can I get rid of this?


texts:
I was reading the data sheet for 1N4007 datasheet for 1N4007 and I noticed that the values for the current (it's not clear from the datasheet, but they probably mean the non-repetitive peak forward surge) is given for resistive and inductive loads only. For capacitive loads, it requires a 20% derating. What is the reason for this? Does it have something to do with the p-n junction?

From what I understand,  for a given current I, the diode requires a voltage drop V(I) (as complex as it can be), thus the power dissipated is I*V(I) and that should determine the max allowed current. This has nothing to do with the external circuitry used to obtain the current I. The only possible explanation I can imagine is that when connected to a capacitor, there is charge leakage into the p-n junction that causes changes. Any thoughts?


texts: Why can't I get maximum gain that can be achieved by LM358 op amps (gain < 3.6 !!!)?

texts:
I need to amplify the PT100 (temperature sensor) for giving it to an  Arduino, so I used this circuit with LM358 (V1 and V2 values are not correct):

The V2 AND V1 came from this circuit (based of Measuring Temperature From PT100 Using Arduino):

So as you can see the gain could be calculated like this:

My circuit is like the above circuit with these values:

R4=R3=10K and R2=3.3K and R1=10K potentiometer this type:

So when I have used the R1=10K I have gained G=(1+2*(3.3/10))=1.66 but when I reduce R1 until 10 I can not get a gain of more than G=3.62 it means that R1=2.5k which is not true and for example R1=10.

I have used the 5V port of Arduino or external 6V power supply but this result have achieved again.

This is the circuit:

Here the VIN+ - VIN- =0.060V (V1=0.147V V2=0.208V, which V2 is PT100 voltage), and the output is V_out=0.201V which the gain is G=(0.201/0.060)=3.35 but the R1=2.8 which with this value:

  gain=(1+2×3300/2.8)=2358.14

Also, the output of V_A1 or V U1:B = 0.120V for input of V1=0.150V &&  V_A2 or V U1:A = 0.156V for input of V1=0.208V  &&  V_U2:A or V_A3=0.201V .

I have double-checked the resistors and LM358 and changed them with another of that type but the result didn't change.

Also, the maximum gain of the LM358 is 100,000 so it must be achievable, so why did this happen?

Edited:

I have added the details as the  @WhatRoughBeast Wanted here:

I have coworker that consist you must use the LM358 with both Positive and negative power supply (i have used only positive voltage for LM358 ICs) So I checked google and seen this question :

  Does op amp need negative voltage?

  As long as the voltage on the op-amp input leads does not become
  negative, the circuit can handle negative input voltages.

So is my coworker rigth?

So what do you think about why did this happen?

Update:

I have one mistake in my measurement, and that was during the measuring I have changed the power supply because of increasing the level of current control in my power supply(and the voltage of power supply changed for almost 1 volt, I don't know why?), so the table have this incorrectness in measurement in last rows. I checked the circuit with negative power supply too, and the circuit worked correctly.

Anyway thanks all for yours attention and yours times.


texts:
I'm trying to do this electronics exercise, but I can't tell if the question is wrong or I have to add something to the circuit.

I have to draw the diode circuit, starting from the input and output voltage graph, and calculate its function:

I've drawn this circuit:

The Vo voltage is the one of R3.

However, the corresponding plot of my circuit is this:

If Vi >= 0.7V, D1 is ON and D2 is OFF. R1 = 3/2 * R3.

If Vi <= -0.7V, D1 is OFF and D2 is ON. R2 = 2 * R3.
EDIT: there is an error here and in the graph, R2 = R3/2

If -0.7V <= Vi <= 0.7V, they are both OFF.

I cannot understand how it is possible to have, as required by the exercise, a positive output voltage when the input voltage is negative.

Thank you


texts: Electrical resistance of two conductors of equal surface area in contact with another?

texts: Resistance of a wire can be determined by the formula R = resistivity*(length/area). What if you have a wire composed of two parallel metals that are in contact with one another? Will the resistivity be a weighted average of the two values of each metal?


texts: Shunt resistor, what value should I expect when soldering on PCB?

texts:
I am using a 10 mohm 1% shunt to measure current via voltage drop.

My circuit is on a breadboard...

It behaves as if the shunt has a value of ~30-40 mohm instead of 10 mohms.
I double checked this by sourcing the current through the shunt alone and reading the voltage drop.
I am pretty sure the source of this extra resistance is from the contact connections to the shunt.

Right now the breadboard circuit is trimmed for a ~30-40 mohm shunt value. My question is should expect to see the correct 10 mohm value when everything solder to a PCB?
If so I need to change up the part selection and PCB component labels.

However, if I should be seeing minimal added resistance from the breadboard connections this could mean they sent me the wrong shunt value or it's defective. I only have 1 unfortunately so I can't verify if it's behaving unexpectedly.

Here are some pictures:

Schematic, Isense+/- connect to the shunt resistor.

Resistance measurement with meter. This is showing 220mOhm, depending on what connectors I use I typical get ~40-50mOhms... the point is its definitely not 10mOhms:

Here's the breadboard bird nest. It's tuned for ~30mOhm shunt. Works accurately and consistently.

Here is the proposed PCB layout. The different ground planes are connected at a star so don't worry about that; I found it was the cleanest way to do it, I don't want to get into a ground plane argument...


texts: Running network cable near X-Ray equipment

texts:
My mother runs a small veterinary clinic. She is getting a new X-Ray machine that will need a network connection to send digital copies of the X-Ray to the server. I will be installing a wall plate with a few Ethernet jacks in the X-Ray room.

Do I need to do anything special like shielded cabling for this install? I am not worried about transmission errors that may occur during the split second the X-Ray is active, TCP can fix those, I am concerned about damaging the NIC card on the computer or router in the wiring closet due to some form of current induction.

The cable will not be running in the direct path of the X-Ray beam just be in wall leading to the room. Am I being overly cautious or is this a legitimate concern? Also if I need to route under the path of the beam for some reason are there any consequences for that?


texts:
I was about to post a question asking for a schematic critique, although while checking things I've noticed a few things on the transistor datasheet that strike me as being a little strange. The datasheet in question is for an NPN, TO-92. The second page states the electrical characteristics, and they're making things a little harder to understand how transistors actually work.

The Vceo and Vces are marked down as minimum values, which would seem to imply that there must be a minimum voltage between the collector and emitter of 45V to 50V depending on the total current passing through the collector. Should these two values be marked as maximum rather than minimum?

Similarly, the Emitter Base Voltage, as I understand is the maximum voltage that can exist between the emitter and base, assuming that the emitter ended up with a positive voltage in reference to the base voltage. So again, should this be marked as maximum rather than minimum?

Finally, the DC Current Gain has a minimum of 100, but this appears for an Ic of 100mA. Am I able to assume that I'll always have a current gain of at least 100, irrelevant of Ic? If not, how am I to know the minimum current gain if I'm not passing in 100mA?

EDIT:
After looking at a different transistor, I've found the 2N5551 from Fairchild Semiconductors, and the respective datasheet. It's far easier to understand, as the parameter names are far less ambiguous. For example Collector-Emitter Breakdown Voltage etc, the keyword being breakdown in the name. Also, they also provide a spice model and plenty of graphs. Seems there's a large difference in the quality of datasheets.


texts:
When I power off and on my device, it draws around 90mA and after sometime (around 1-2 min), the current value drops to around 40mA-50mA.

Is it because some of the ICs go into standby mode after a period of inactivity?


texts: How do I know whether a fuse is a DC fuse or an AC fuse?

texts: For example, I want to buy a 10A 50V DC fuse and a 10A 220V AC fuse online. Which website(s) should I go ? I tried on Mcmaster, but I could not get clear enough information of whether the fuse is an AC type or DC type


texts: Noob question here. Why would the term \$j2\pi t\$ not have any effect on the energy of the signal?


texts: Suggestion about Peltier Efficiency With Current Power Setup

texts:
I am currently using the very arbitrary TES1-4902 to cool water (small amounts) using a 5V 2.4A USB Battery Pack (2 Peltiers TES1-4902, 2 5V 2.4 A USB Battery Packs = 5V 4.8A)

Recently, it has come to my attention that a different Peltier setup may be able to increase my efficiency, thus giving me more "bang for my buck".

The current situation that I am in is that I need to achieve the maximum cooling power to cool small amounts of water as quick as possible; however, I need to reduce power consumption so that instead of buying two 5v 2.4A USB battery packs I can buy 1, 3.4 A USB battery pack to support my project and thus reduce my price.

I know that the more power you put into a peltier, the cooler it gets, so less power is counter-intuitive: so I will split my question into two parts:

1) Is there a more efficient Peltier (where the rated IMAX/VMAX/DT is more efficient than what I have) that runs on a 5V 2.4A batterry, that takes into account more power is needed to start the Peltier than to run it continuously?

How about a 5v 4.8A  battery?

2) Using a 3.4 AMP, 5V USB Battery pack, is there any way I can achieve a similar cooling effect than what I currently have (TES1-4902, 5V 4.8A (2 of them)? by using a more efficient peltier?

Thank you so much, while someone answers me I am learning how to read data sheets more efficiently; however, so many of you are much more knowledgeable than me I thought it may be useful to ask you guys who have been so helpful in the past.

Thanks!!!


texts: What is the difference between these ring oscillator topologies? How can I simulate one without "noise voltage?"

texts:
If I understand correctly, with ring oscillator, it adds the negative feedback back to the loop to make a supposedly infinite gain. With the first topology (NMOS inverter) the negative feedback adds to each stage delay because of transfer function H(w), adding infinity gain with each loop.

But I don't quite understand the other 2 design, the CMOS inverter and the differrential ring oscillator.

And does anyone know how to  test the circuit? Do I have to add some "noise voltage" or  is there anyway to make it work loop immediately and create oscillation without any activation voltage?


texts: How to select a common mode choke inductance value for power supply EMC filter design?

texts:
I would like to know how to select a common mode choke inductance value for EMC filter design for DC -DC power supply
The Specifications are :
Cutoff frequency : 20 Khz
Power suppply Maximum Current : 2A
Power suppply voltage : 24V
Required Impedence : Maximum Noise must be attenuated.
EMC test Environment immision : 450 Mhz
I am learning about power supplies , EMC Filters so kindly help me in this so that it would be a helpfull for my knowledge.
Thanks


texts:
I want to know is possible cooling a box in 1 * 2 m size by peltier?
please help me
thanks


texts:
I am using a 12V LED for blinking purpose. Whenever it gets a signal from source(indicating the emission of rays), it blinks. The signal voltage out of the source is 5V. The supply to the source is 24V. I am using a relay in between the source and the LED.

Whenever the source is triggered, the signal from the source triggers the relay and in turn LED blinks.The challenge i am facing right now is:
If the LED fails, the source should not emit the rays itself. Basically it should check whether the led is working or not and then signal should come out from the source. If the led is not working even though the source is triggered, the source should not emit the rays. How can i achieve it? Is it possible with a relay or a led with feedback circuit or any other? Thanks in advance.


texts: Positive feedback with constant transfer functions

texts:
If I have a control loop with positive feedback, the closed loop transfer function expression is: $$\frac{Y(s)}{X(s)} = \frac{P(s)}{1-P(s)H(s)} $$
where  \$P(s)\$  is the direct loop transfer function and \$H(s)\$ is the feedback one. I know that in this scenario the stability (or instability) of the closed loop depends entirely on the zeros of $$ 1 - P(s)H(s) $$ But what if both \$P\$ and \$H\$ are constants greater than \$1\$? In that scenario my intuition tells me that the system should be unstable given that every input would appear at the output scaled by a factor,  then multiplied again to be added with the input to be scaled again and so on. So the output would go to infinity. But if I follow the closed loop transfer function  the output has a fixed negative value for a positive input given by:  $$ y(t) = \frac{p}{1-ph} x(t) $$
How is this possible? I simulated it with Simulink and it is consistent with the closed loop transfer, but I can't understand how I can get a negative output multiplying and adding positive things in a loop.

What am I missing here?


texts: Why are solderless protoboards called "breadboards"?  I've used the term for decades but couldn't answer a student's question about the name.


texts: Line level audio output from headphones level output

texts:
I am new to analog audio interface design. I am trying to get a line level output from a amplified headphones level output. I want both of the output to work at the same time in order for the user to be able to listen through headphones while recording the line level output.

Would something like this work ? (coupling capacitors not included):

I1 being the output of my headphones amplifier, R4 or R5 being a pot to adjust the line level output.

My guess is that the high-Z input of the opamp will not disturb the headphones output but I also wonder if the headphones amplifier can fry the opamp if the headphones are not connected.

I could have taken the line level output before the amplifier but the input of the amplifier will most likely be differential audio and it makes it a bit more complicated for me.

I would like to have advice on whether or not this can be a suitable circuit and also what are the best practices and/or things to avoid when it comes to analog audio interface.


texts: Considerations in a bench/lab power supply?

texts:
I'm looking at adding a low-cost variable power supply to my electronics hobby bench. After years of cobbling together LM317's and LM7805's, it's about time...

Considerations:

I've found a few options which I am unsure about.

Dave at EEVBlog states in various videos (#8, #30, #166 (@04:16), #168, #272, #314) that you should look for the following:

Multi-turn knobs for voltage and current adjustment (as opposed to pushbuttons and separate coarse/fine knobs)
A power supply that can range from 0 volts on the low end instead of 1 or 1.2 volts
A switch to turn on/off the load
The supply shouldn't overshoot the target voltage when switched on
It should have a separate mains earth ground terminal (to allow combining supplies)
Prefer linear for less ripple and noise (though switching offers smaller size and cost for higher currents)

Of course some factors depend on the intended use, some depend on preference, and some depend on budget.

(My intended usage is primarily microcontroller projects (3.3V-5V, <1A), automation and control projects (solenoid, stepper motor, etc) (12-24V, <5A), and low voltage lighting projects (12-24V, <3A). Budget ideally < $300.)

I asked earlier about the last point, linear vs switching, in a previous question. Olin convinced me that the disadvantages of a switching supply are minor, and certainly for my application, make sense for budget, bench space, and other reasons.

Thoughts:

To touch on the other points:

Multi-turn pots must be preference. I think they are better than single-turn pots, but I would prefer coarse/fine adjustments (or direct-entry via buttons) over turning a knob multiple times to make a larger adjustments.
I haven't needed to work on projects below 3.3 volts, but I am mindful of the pico-power AVR micros, which can run at 0.7V. Certainly a supply that can go below 1 volt would be useful for this.
A load switch is nice, but not a deal-breaker.
How essential is it to have separate earth ground? I don't think I need to combine power supplies.

Possible Supplies:

I've found a few supplies that I like, but I can't commit because none meet all the criteria.

BK Precision 1550, 1-36V 0-3A, $150. Concerns: Doesn't go below 1 volt. Uses up/down buttons for adjustment.
Circuit Specialists CSI3005X5, 0-30V, 0-5A, $130. Concerns: Unfamiliar brand and low price. (quality issue?)
BK Precision 1671A, 0-30V 0-5A, $220. Concerns: Unknown adjustment turns; no earth ground terminal.

Is there some other supply or brand that meets all of these requirements? What points (if any) above, are truly important?


texts: What would cause a 120 VAC universal motor to run slower in reverse?

texts:
I got a bargain on a few small universal motor that run on 120VAC and I'm trying to reverse the direction. I don't have a lot of experience with these types of motors but I do know they run on AC or DC and the direction can usually be reversed by simply swapping the wires on the brushes. On this particular motor swapping the wires to the brushes does reverse the direction but the RPM is slowed to about 1/3 of that in the forward direction. I have read that manufacturers sometimes tune the placement of the brushes to reduce inductive reactance but I'm not sure how to confirm if this is the case or what to do if it is. The schematic below shows my current test setup. I added a DPDT switch to be able to reverse the direction easily but my goal is to run it in reverse only. There are two small inductors on the outputs of the field windings just before the brushes but I assume these are just for tuning and would not be the cause of the issue but I could be wrong ( they appear to be identical on both sides but I have not measured them).

Is there anything I'm missing that would cause the motor to run slower in reverse or anything I can try to resolve the issue?

Motor Schematic

Motor view 1

Motor view 2

Motor view 3

Motor view 4 (tuning inductors)


texts: What is the effect on noise immunity of a floating shield on a shielded twisted pair

texts:
We have an installed system where resistive sensors are connected to some electronics by shielded cables of between 2 and 10 metres. The cable is a twisted pair sheathed in a stainless steel braid.  At the sensor end, the braid is unconnected, and the sensor is wired to each leg of the pair.  At the other end (the electronics) the braid is unconnected, one leg of the pair goes to the electronics ground, and one leg is switched at some 100's of kHz between digital supply and ground.  The resistance of the sensor is measured by charge-balancing techniques.

My question(s):

How much better is this configuration (a floating shield) better than no shield at all?

How much worse is this configuration than one where the braid is grounded at the electronics end (which was the intended topology)?

Footnote: the issue I am investigating is one of hardware unreliability caused by possible noise injection over a 5 metre run of the above-described cabling.  The environment is a laboratory with a likelihood of motors in refrigeration units switching off and on. The Ethernet-connected nodes occasionally become unresponsive and I am wondering what the potential is for larger voltage spikes being introduced to the nodes (or to the PC connected to the same network).


texts: Relay to control the power rail on a PCI adapter

texts: I am trying to find a relay which will control the 12V power rail of a PCIe adapter so I can cycle power to a device during testing.  The relay should be normally closed.  I plan to control the relay using a GPIO from a Raspberry Pi so the signal should be 3.3V.  I have tried looking digikey and narrowing down the search criteria, but I can't seem to find one.  If one doesn't exist, what would it take to create a switch using components (i.e., MOSFETs).  Thanks.


texts:
I am making a GSM + GPS Board, and we don't want to put an external antenna on top of it via any sort of connection.

Primariliy to reduce the cost. I've seen a VTS system with an onboard antenna which gives good enough signal even when the unit is in the basement or indoors.

Now i am not getting any sample reference or guides to work on it. Anyone can point me a guide / pdf / page where these things are xplained ?

We dont want to purchase an antenna we want to have an antenna on our PCB board itself.

Here's a Picture of the Antenna


texts: Use of READY line on 8086 - is it mandatory?

texts:
Alright folks,

I've recently begun working through the design of an 8086 single-board in my free time to play with (for lack of a better word, I need to experience the rush of being close to low-level hardware again).

I had the intention of using 35ns-capable MRAM as a storage medium (program code/RAM) mainly as an experiment, but also because I have some devices laying around unsoldered. I've checked the datasheets and the device (MR2A16A) carries SRAM-compatible timing - it doesn't specify a max on its access timings, so initial thoughts are to give it a try.

The issue is that according to the datasheet, the 8086 uses the READY line as a signal to remove its bus (AD15-AD0) from the high-impedance state and read in the data (or at least, that's what I'm given to believe). Below is the section detailed "System Timing - Minimum Mode". It can be found here on page 12:

  The read cycle begins in T1 with the assertion of the Address Latch Enable (ALE) signal. The trailing (low-going) edge of this signal is used to latch the address information, which is valid on the local bus at this time, into the address latch. The BHE# and A0 address the low, high, or both bytes. From T1 to T4 the M/IO# signal indicates a memory or I/O operation. At T2 the address is removed from the local bus and the bus goes to a high-impedance state. The read control signal is also asserted at T2. The read (RD#) signal causes the addressed device to enable its data bus drivers to the local bus. Some time later valid data will be available on the bus and the addressed device will drive the READY line HIGH. When the processor returns the read signal to a HIGH level, the addressed device will again 3-state its bus drivers. If a transceiver is required to buffer the 8086 local bus, signals DT/R# and DEN# are provided by the 8086.

Obviously, no memory controller nowadays is going to rely on a discrete signal that tells it when data has appeared. Its timing simply agrees with the memory. As such, this MRAM has no such signal.

To further complicate matters, the diagrams prior to page 12 for examples of the minimum/maximum mode hardware configurations only show READY being used by the clock and reset generator logic, but the memory and local bus is not utilizing it whatsoever.

So, final question being, is this line even necessary for memory access? Am I even getting its function correct? Please advise.


texts: I've used this website to figure out how to wire up an LED project I am going to do, the only thing I'm not convinced by is the fact that on this diagram they have supplied me the resistors are after the LEDs. Is this correct, is this wrong, or am I just reading it wrong. I am reading it as I have 3 parallel sets of 4 LEDs in series with the resistors on the negative end of each set.


texts:
I have a tiny 8 ohm speaker rated to accept a maximum of 0.5W. The docs explicitly say adding 1.5W or more will "blow it out".

However, I'd like to use this speaker with a 1.5W amplifier (PAM8302A). Can I safely use this with the speaker by adding about 16 ohms of resistance in series with the speaker?


texts: Telescopic cascode operational amplifier: why not rail the bias nodes?

texts:
In a fully differential telescopic cascode opamp, there is a bias voltage for two of the nMOSFETs whose gates are tied together and a bias voltage for two of the pMOSFETs whose gates are tied together. Why wouldn't the nMOSFETs' gates be tied to Vdd and the pMOSFETs' gates tied to ground?

Edit: Sorry for being vague, folks, I was posting this question from my phone last night so a) I didn't have the schematic I wanted, and b) I was tired and left out a critical detail: yes, telescopic cascode op-amp is what I'm referencing. Specifically, I'm talking about the Vbn and Vbp nodes from the figure below.


texts: How can I simulate contamination delay in VHDL?

texts:
Propagation delay is simple to implement:

  Out <= '1' after 3ns;

I tried to add contamination delay as such:

Out <= '1' after 3ns;
Out <= 'X' after 1ns;

so that Out would become undefined and then switch properly. However, in simulation I only observe the final assignment. [I'm using MultiSim to simulate, but this Quartus II link suggests it's normal to only observe the final assignment]

Is there a good way to simulate contamination delay?


texts: I have an N-MOSFET array IC and I don't need to use all of them, but I do need to use a diode. Is it OK to use the body diode of one of the MOSFETs as a regular diode to decrease component count and footprint? Can I just tie source to gate and use the MOSFET in place of a diode in the circuit?


texts: What are the capacitor values and why there are holes in PCB? - Semtech's reference design - SX1272MB1DCS

texts:
Semtech is providing a reference design concerning the SX1272 chip:

SX1272 modules: SX1272MB1DCS - 868 MHz - Combined RFI and RFO, switchless (Ref design only)

I can't find the values of C12, C14, C19 and C20 capacitors in the bill of materials.
These should be somehow calculated or what?

Moreover, there are 0R resistors, what are they for?

And what are the holes in PCB for? Are they necessary?

Sorry, if this question is trivial. I never designed antenna's part of PCB.


texts: Replacing 18650 Cells in a laptop Battery

texts:
Is it possible to reconstruct a battery of a laptop with better quality 18650 Cells than that are used by the  OEM Manufacturers. eg i have a MSI ge62 6qf with rubbed off LG cells so i cant tell what MAH they are but the battery is designed for 4700-4900mAh. Since i cant buy an OEM battery in my country and it is like impossible to import as a battery will cost 3 times of the said item to import it. So here comes my idea since i have a spot welder in my university and i can buy good quality Panasonic NCR18650B 3400 mAh, can i replace them in the laptop battery

What will be the issues and problems related to the battery Construction except being extra careful in spot welding.
What are also the general concepts related to replacing 18650 Cells
are laptop cells protected like the ones offered in the market or they dont have protection
what is the Role of the controllers in each of battery
any help would be appreciated