texts: When has an embedded PC finished its shutdown process?

texts:
We have a product that has a PC running on a small board.  Our product generally runs for weeks, if not months.  One thing that is not very well implemented is the shutdown process.  The device does not have a screen so the user cannot see the shutdown progress.

Is there a feature on Embedded PC's (smaller form factor MB's like MiniATX, MicroATX etc) that provides a hardware indication that the OS has completed the shutdown process or more specifically that power is needed/not-needed?


texts: What can be the advantages of using "normal" trigger mode in an oscilloscope?

texts:
I'm not an advanced scope user and almost all the time I use it in Auto trigger mode. What I know about the normal mode is that if the trigger level is outside of the signal range the signal on the screen disappears(analog scope) or freezes(DSO).

But in what situations would normal mode be used in practice?


texts: How does load resistance affect the function of this crystal oscillator?

texts:
Related

Load Resistor across Crystal - though that's for a passive crystal and not an integrated XO.

Summary

I'm considering using an Epson TG-5035C XO and am figuring out the circuit necessary to couple it to an Atmel AT89LP428.

Oscillator Specs

The XO shows these specs for the passives to connect:

I assume that the "DC cut capacitor" is a coupling, or DC block, capacitor to be inserted inline between the output of the oscillator and the XTAL1 crystal amp input of the MCU.

Microcontroller Specs

The MCU shows this connection diagram:

which is only partially applicable in my case. As determined in a previous question, XTAL2 will be left open, and the output of the XO will go through a 10nF cap to XTAL1.

What I don't know how to handle is the load resistance. The XO shows it as a load "condition" of 10k, and I don't know whether that's an equality requirement, a minimum, a maximum, or simply what they tested at - and if it's what they tested at, it's not clear which other values on the specsheet rely on that 10k.

Most other literature on crystal oscillators that I've read suggest a load resistor in the 1-5Mohm range, and the MCU spec agrees. So which makes more sense in this scenario - a 10k or a 4.7M load resistor?


texts: How to calculate voltage across each resistor in a chain for a given tolerance?

texts:
I have a chain of 24 0603 resistors with about 1600V across them, how do I calculate the worst-case voltage across them with a given tolerance? I'm not sure whether to use 3%, 1%, or 0.1%, etc.

(Schematic only has four just to illustrate the idea)

simulate this circuit – Schematic created using CircuitLab


texts:
I have a design with the ADM2587 in half duplex mode:

If I want to receive something over RS485 I pull RE and DE low. This is tested and works good.
The same thing with sending: RE and DE high, sending works, everybody is happy.

Now, sometimes I want to work directly with the UART on the board (the RX and TX lines feeding into the ADM2587). This is where stuff gets tricky.
To use the UART, I have to do the opposite: for receiving I have to pull RE and DE high, for sending RE and DE low. If I do anything else the ADM seems to pull on it's RX and TX lines, and my microcontroller is not able to communicate properly.

Do I something wrong, or can ADM really not coexist with some other serial communication on it's input lines?? In my ideal dream world, I would have RE constantly low (enabling the receiver), and DE normally low to keep my uart communication on the board. Only if I want to send something out I would enable DE and send data over RS485.

But this results in chaos and mayhem. RS485 is not stable (many bit errors in communication due to wrong voltage levels) and UART doesn't work at all (I can see the received data on the lines, but the LOW voltage does only go to 3V, not all the way down to 0V).

Picture below: RX Signal on the microcontroller pin, RE LOW, DE LOW

Any ideas? how would one implement an "receive only" ADM25XX, where the lines are not held by the chip?


texts: Is it safe to drive a MOSFET from an output pin of a microcontroller?

texts:
I have used commonly-available BJTs such as the 2N2222 and 2N3904 as switches by operating them in "saturation mode" from my MCU. I believe, however, that for these sorts of applications, a MOSFET is a more appropriate device. I have a few questions, however.

1) Does a MOSFET have a "saturation mode" like the BJT does? Is this "saturation" achieved by simply providing a high enough voltage on the base that the MOSFET is completely "on"?

2) Is it safe to drive the MOSFET directly from the MCU? I understand that the gate of the MOSFET behaves like a capacitor, and therefore draws some current while "charging", and then none thereafter. Is this charging current high enough to damage the MCU pin? By placing a resistor in series with the gate, I can protect the pin, but this will slow down the switch, possibly resulting in high heat dissipation by the MOSFET?

3) What is a common "hobbyist" MOSFET suitable for various low-power situation? I.E., what's the MOSFET equivalent to a 2N2222 or 2N3904?


texts: How to find out if a microprocessor is powerful enough

texts:
Everybody knows its easy to develop a proof of concept for an embedded device on a rasbperry pi or even a PC, although when it comes down to choosing a microprocessor for your product, it is difficult to be sure your choice will allow your concept to work optimally.

I currently have a media streaming project successfully working on the raspberry pi, although the pi is much to big and bulky for it to be proper as an end device.  Also it is stated that the end device is custom.  I'm having a hard time finding confidence in processors that I can use.

What is a good process as to finding out if a processor is powerful enough to run my application?

Basically my requirements are:

USB host or embedded TCP/IP stack for WiFi operation
I2S/PCM media protocol
I2C for peripheral configuration

Finding chips with those properties is very very simply.  It honestly couldn't be simpler.  The issue is being able to tell if the chip is fast enough, processing and operation-wise.

I've looked at the LPC4337 quite a bit and I feel like it would be suitable although the development environment is giving me quite a bit of trouble, for that reason I'm still looking around, which led me to the CC3200 from Texas Instruments, although that controller only runs at 80 MHz and I'm not sure if that will be strong enough for real-time media streaming.

What are some steps to make sure a processor is fast enough for my application?  Like how do I know if an 80 MHz processor will be good enough or do I need something on the order of 204 MHz or even higher?


texts: AC-Coupling blocking negative voltage values

texts:
This question is about the amplification of an electret microphone signal

In this video: https://www.youtube.com/watch?v=SToBPCajwc0&t=615s

He is using an AC-Coupling capacitor to block the DC component and then a transistor to amplify the signal.

At the 9:20 mark, he says that the negative voltage values would be cut off after going through the AC-Coupling Capacitor. I can't think why AC-Coupling would block negative values. Is it actually that the transistor would block the negative values? Or is he thinking further ahead about an ADC on a soundcard not accepting negative voltage signal values?


texts: 2N7000 NMOS only switches properly when gate and source is connected with 1MΩ

texts:
I am building a circuit on a breadboard to see if I can get a 2N7000 NMOS to switch using a 3.3V V_gs signal. As far as I know, I've set up the circuit properly:

simulate this circuit – Schematic created using CircuitLab

However,

This circuit causes the LED to light up regardless if V_gs is 3.3V or 0V. The transistor conducts no matter what.
It works properly when I connect a 1MΩ resistor between Gate and Source. Now, when V_gs is 0V, the LED turns off and when V_gs is 3.3V, the LED turns on. I discovered this when I was probing Gate and Source with a multimeter, and I wondered if an 1MΩ resistor would achieve the same effect.

Can someone explain this phenomenon for me? Thank you very much.


texts: How to let capacitor fully charged before being discharged by a load?

texts: I having a problem to allow a supercap to be fully charged before being discharge by a 0.9V to 5V booster. Here is my situation, I am using TEG to charge a cap to 2.3V, I am able to do that if i disconnect the 0.9V to 5V booster. However, if i connect the booster, it will discharge my superCap when it is charged up to 0.9V. Anyway to allow my supercap to be fully charged to 2.3V before being discharged completely ? Based on the diagram, I want my microController to be active for around 10 seconds to complete a task. If the superCap always being discharged at 0.9V, my microController only active for 1 second then go back off mode. Anyone has idea ?? I'm doing energy harvesting topic, I hope not to use any external power source like batteries. Thanks in advance.


texts: From what organization or document are connector symbols like this referenced?

texts: So in this picture I am asking about the representation of the Plug and Jack. Where does the idea that the plug is rounded on the back side come from? I am trying to put together a best practices doc fo work and was asked for some backup as to who made that standard and I cant find an explanation.


texts: Understanding electric DC gear motor for project

texts:
I would like to build an Arduino controlled coin sorter and counter. I want to use a spinning angled disk with holes in them to pick up individual coins.

I have been looking at some 3V DC geared motors on Ebay. I understand that high torque will be important so that it will be able to turn the disk with money pushing against the disk.

How will I find out if a 5-8 RPM motor will be able to turn the disk? These small motors usually have no torque measurement given.

Is there even a DC motor that runs at 3V that would be able to turn the disk?


texts: ENC28J60 Custom board, heat and performance issues. need input

texts:
So since the last post I made regarding the differential line matching on a custom board HERE I have finished the board and started using it. the enc28j60 chip works as expected and i get around 2.3 Mbps average up and download speed. My problem is chip got so hot that i could not touch it for longer then 3 seconds. I looked through the schematic again and can not find the issue. I then blindly started removing components, checking values trying to understand what is going on. I then got to the ferrite bead on the center tap of the RJ45 Jack.( see L1 in the schematic )

After completely removing L1 the heat was atleast 40% decreased while running but a side effect was that im now getting 12Mbps download speed and 14 Mbps upload speed (see image attached). Ever since I removed the L1 the Actively lights on the Magjack stopped working.

Can someone shed some light on what is happening here ?


texts:
I am using pj-102ah dc barrel jack. I am not sure if this is a mistake in the dimensions, or you can correct me if I am wrong. the top left red circle shows the the length of the three pins which is 1mm, while the bottom red circle shows the length X width which is 1mm X 1.6mm. How come the width is more than the length, and it seems wrong even from the real picture of the jack.

I updated the footprint as shown in the picture above, where the white squares represent the drills for the pins.


texts: If I need to send GPRS commands is it better to use a "proper" modem, arduino or a mobile?

texts:
I need to send some commands from a computer via GPRS protocol to some devices.

The options I have found so far are:

Commercial GPRS modem
Arduino GPRS shield
an old phone as GPRS modem

Is there any limitation if i use the Arduino or an old phone?

Or should I buy the "real" modem?

I need the solution to be very reliable.

PD, if this is not the right place on stackExchange, please let me know where to post it.
Cheers


texts: Charging 12V Battery from AC-DC Converter

texts:
I am planning to charge my 12V sealed Lead Acid battery from AC to DC Converter. The output of the AC-DC Converter is adjustable so that I can set my voltage to be 14.7V(considering diode voltage drop) in order to charge the battery. The resistor 10 Ω is used to limit the charge current of 210mA.12V is mainly used to drive fan and other small circuits

My questions :

1.Once the battery is fully charged, the output across the battery  would be 12.7V.I do not want to disconnect the battery or switch it over the float charging (13.6V) as I want my design to keep it simple. My only concern is overcharging the battery if left connected. Does it have any impact on its life. Do I need specific charging circuitry to charge the lead acid battery.

2.In case of power failure ,my battery delivers the power required to the system. Since my voltage regulator requires minimum input voltage greater than 2V of expected output, my Linear regulator does not work. So I have to modify my design to use either LDO /Switching regulator. Another option is give the unregulated output of the battery to my fan(it can work anywhere from 10V) during normal conditions. So I can power small circuits using 5V.
Does it work perfectly?Please give ur suugestions.


texts: 10x 3w led lights to run off 12v battery

texts:
i have ten 3w leds i need to build an array to run from a 12v car battery.

Led (forward voltage 3.6) (forward current 700 ma )
(Source voltage 12-13.9)

Will this work and if it will what wattage does the registers need to be?
if not can you help with a design that will. Thank You


texts: Powering multiple LED strips with one power supply via termina connectors

texts:
I bought a power supply so I can start experimenting with larger arrays of LED strips at home (I was previously using a wall wart with a small display).  The power supply provides 40A at 5V, however, the power supply only has one + and one – terminal.  How can I safely split the current to multiple strips?  I am looking at terminal connectors:

http://www.amazon.com/Blue-Sea-Systems-Circuit-Terminal/dp/B000K2K6L6/ref=pd_bxgy_200_3?ie=UTF8&refRID=0HDQC12FCR3V0GJ967X

but I only see them rated for 30A at maximum.  I would feel better if they were rated much higher than 40A.  Somebody told me I could daisy chain them together but it seems like I would still need to pass 40A through the first one.  Would it be better to use a bus bar?  Also, can you recommend a fuse?


texts: Can a cathode tube light be run off a battery?

texts:
I have two cathode tubes I bought for my computer case back in the day. they are the standard sata connection to the PSU.

My question is can I change the plug end that of a 9V battery or is this simply not enough juice? Or if I where to wire it up to a main sock in the UK (240V) what would I need to do to stop the excess. Is mains a total bad idea?


texts: Class A power amplifier: power dissipation

texts:
Let's consider the following class A power amplifier:

And here is the time-domain simulation of the power dissipated across the transistor:

As we can see, the power varies from approx \$0.1W\$ to \$1W\$. How can we interpret this?


texts:
For a project that I've been working on, I want to drive a couple of ICs and several LEDs from an ~12V supply (lead-acid battery). I think the whole thing should draw about 100mA, so I didn't really want to use a linear regulator: I shouldn't need to dissipate 1.2 watts just to drive a couple of LEDs!

So I designed things with a buck converter based on an MC33063 chip and I've been breadboarding to see how everything works. Unfortunately, what I should have realised before is that I can't avoid discontinuous mode with such low current draw and such a large step down in voltage. Trying 3.3V output, the regulator switches on and off at about 500Hz giving an unpleasant sounding buzz from the inductor and a spectacularly poor output waveform (~1V ripple). I'm using a 50 Ohm load, which should draw about 50mA.

Am I just "Doing It Wrong"? If so, what's the sensible solution I've missed? I guess I could follow the buck regulator with an LDO to filter the power rail, but that's getting a bit ridiculous and won't help with the unpleasant sound from the inductor being switched on and off. Ideas?

There's not much to see, but the buck portion of the circuit is just this:

.

When breadboarding, I've replaced R2 with a dead short because I don't have any low value through-hole resistors, but I shouldn't imagine that makes much difference (since it's a high current cut-out). D1 is an SR104 Schottky.


texts: Why is an aluminium coat added before the catalyst for CNT growth by CVD?

texts:
A lecturer has told me that one particular method of CNT synthesis on Si substrates makes use of aluminium across one pair of electrodes and iron across the other. The substrate and the electrodes are pumped down to a very high vacuum. The first set of electrodes pass current and the aluminium is vaporised and deposited onto the substrate. The same follows for the iron.

I understand why Fe is deposited. This is well written about.

Why is the aluminium deposited though?


texts: Is this a capacitor or a varistor? How can I figure out specifics?


texts:
I know its basic but google just doesn't give me anything .

I have Eagle on a mac, i have a design with a few resistors, i would like to change their footprint to 0805 .

The menu is just not showing me this option to see the part footprint.

thank you.


texts: Powering multiple led strips by one switch

texts:
I have a problem I cannot figure out. I have this circuit which should control two LED strips either by wemos OR (methods are switched between by SPDT because I don't know automatic way) manually. Each "switch" should be able to turn on one or both leds.
Circuit details
Wemos uses two N-mosfets (irlml2502) to turn on/off leds. Manually I turn them on/off by SPDT switch.
Circuit is powered by 12V adapter going to the LEDs and buck-converter to convert to 5V to power wemos. To separate LEDs powering I use Schottky diode SB540.
PROBLEM
The problem is, when I use manual switch, it turns on both of the leds everytime. Also, the buck-converter´s power led is ON on that time but the IN- is not connected to anything.
Even when I connect ground to buck-converter IN- both ledstrips are turned ON.
As I understand it, ground to the mosfets should flow through buck-converter but it is flowing flowing somewhere else.
Only thing I can think of is that MOSFETs are allowing ground to flow "backwards" from drain to source and power the circuit through each other.
Could you please help me fix the circuit?
Picture description

Circuit is not powered on pictures.
Purple colour shows the ground when I want to power single ledstrip.
Turquoise should power both strips.
Bold black wire upper-right is manual switch 2 and blue is manual switch 1. Curved blue on the right side is ground.
In schematics I ignore buck converter and wemos pins output to mosfets.

simulate this circuit – Schematic created using CircuitLab


texts:
I recently received an Atera DE2 board with a Cyclone II FPGA. I have been experimenting with the expansion headers and I am having trouble understanding why my daughter card is not receiving any power. My DMM is reading 3.3 volts (when I connect the first JP0 pin and ground pins with logic code below), however, the voltage actually drops to something like .6V when it is connected. If I connect the constant VCC 3.3 volt pin and GND it works with no problem.

The extremely basic code:

library ieee;
use ieee.std_logic_1164.all;

entity expansion is
port(
a : in std_logic;
y : out std_logic
);
end entity expansion;

architecture when_else of expansion is
begin
y <= a;
end architecture when_else;

--Pin Assignment
  a = PIN_N25
  y = PIN_D25


texts: MC74HC165N + Arduino, Dunno what's the issue

texts:
I connected the 74HC165 as per this schematic http://dlnmh9ip6v2uc.cloudfront.net/datasheets/BreakoutBoards/SN74HC165%20Shift-In%20Breakout-v11.pdf and then used this code http://playground.arduino.cc/Code/ShiftRegSN74HC165N with NUMBER_OF_SHIFT_CHIPS set to 1. I get all the weird outputs like:

*Pin value change detected*
Pin States:
  Pin-0: LOW
  Pin-1: LOW
  Pin-2: LOW
  Pin-3: LOW
  Pin-4: LOW
  Pin-5: LOW
  Pin-6: LOW
  Pin-7: LOW

*Pin value change detected*
Pin States:
  Pin-0: HIGH
  Pin-1: HIGH
  Pin-2: HIGH
  Pin-3: HIGH
  Pin-4: HIGH
  Pin-5: HIGH
  Pin-6: HIGH
  Pin-7: HIGH

*Pin value change detected*
Pin States:
  Pin-0: LOW
  Pin-1: LOW
  Pin-2: HIGH
  Pin-3: LOW
  Pin-4: HIGH
  Pin-5: HIGH
  Pin-6: HIGH
  Pin-7: HIGH

*Pin value change detected*
Pin States:
  Pin-0: HIGH
  Pin-1: HIGH
  Pin-2: HIGH
  Pin-3: HIGH
  Pin-4: HIGH
  Pin-5: HIGH
  Pin-6: HIGH
  Pin-7: HIGH

*Pin value change detected*
Pin States:
  Pin-0: HIGH
  Pin-1: LOW
  Pin-2: LOW
  Pin-3: LOW
  Pin-4: LOW
  Pin-5: LOW
  Pin-6: LOW
  Pin-7: LOW

*Pin value change detected*
Pin States:
  Pin-0: LOW
  Pin-1: LOW
  Pin-2: LOW
  Pin-3: LOW
  Pin-4: LOW
  Pin-5: LOW
  Pin-6: LOW
  Pin-7: LOW

I have nothing connected to the input pins of the 165. The worst part is, I get the same output even if nothing is connected to the board... :( however the board seems to be okay with other programs, it's a leonardo compatible board.


texts: Custom ATMEGA2560 with RS-232 Communication Problem

texts:
I made a custom PCB using ATMEGA2560 with 2 MAX3223 RS-232 ICs (because they were available to me) but only one Tx channel is working on both ICs and I can't receive anything on any of them. I tried all the baud rates but no change, since I was suspecting the MCU was not working at 16 MHz. But everything else works fine.

U3 on the left is working without auto-shutdown mode and U4 on the right is working in auto-shutdown mode. I was suspecting the auto-shutdown feature, but no difference as both are having issues. Maybe I missed something, but it's been a week now and I can't figure out what.
Just a note that I bought these ICs from Aliexpress. I do have MAX3225 from Mouser with same footprint. Can I replace MAX3223 with MAX3225 if the IC is bad?
Update: So i did the loopback test with 2 usb to uart cables and it looks like one channel in each IC(max3223) is working perfectly (transmit & receive both).
Second channel is outputting nothing but i plan on connecting the oscilloscope and see what's the result there.


texts: Does wireless charging degrade battery life?

texts:
Does a design using wireless charging such as QI effect the longevity/health of lithium-ion batteries such as those found in modern consumer electronics devices?

What special considerations must be taken when incorporating wireless charging into a device to keep the batteries at optimal health?


texts:
I have a slow cooker crock pot thats uses 120 volts AC which range from 0.6 amps to 2 amps and consume electricity that ranges from 70 watts (low temperature) to 250 watts (high temperature). When I look at the label on the bottom of the slow cooker, it says AC current only.

I have a 105 amp 12 volt marine deep cycle battery and an 1100 watt power inverter and a 6 gauge wire that connects the two.

I have a very limited knowledge with electrical appliances and I was wondering does the label mean I can only use AC power and I cannot use a battery powered inverter? Or does it mean it uses that many amps if it is using 120 volt AC power.

Picture of label
https://photos.app.goo.gl/jKnHZmaqxXZ56UDx8


texts: Removing GND cause less bright led but continue working

texts:
simulate this circuit – Schematic created using CircuitLab

U2 is a Max7219 + 2 x 7 segments display 0.56''.

Is my wiring circuit right? Btw I have some question to ask you expert.

1) Per datasheet of LM7805

in input I need to use a ceramic 0.33uF, I have only a 0.22uF electrolyitic. Could be "the same" ?

2) If I remove the GND between Arduino and the VREG, after 3/4 seconds display goes totally off. Is capacitors effect to mantain some last current for the MAX?

3) If I remove the GND between Arduino and MAX7219, the LED becom sensibly less bright, but it works anyway. Why?

Thank you very much


texts:
I have balanced star three phase generator 380V with junction point is connected to ground
And current through from junction point to ground is I0=0 for that clearly say it is balanced system
when i cut off junction point from grounding that apear 30V in junction point
Why that voltage appear? Through it is balanced??

It may question for power engineering


texts: Resistive load (voltage and current monitoring)

texts:
I would like to design a circuit to drive a resistive load (around 3 to 4 ohms) with a maximum current of 2 amps. I want to monitor both voltage and current delivered to the resistive load.

I have designed a first version of the circuit with PWM (20kHz) and a Mosfet. I use a voltage divider to monitor the voltage and an INA169 for the current.

However, voltage and current measurements contain the PWM signal. I tried to filter the outputs, but the result is not very accurate.

Does someone have a better solution to do the monitoring ? Is it possible not to use PWM without dissipating too much energy ?


texts: The channel formed in a MOSFET which is ON consists of carriers. From where do theses carriers come? Do they come from the Source/Drain regions? Thanks.


texts: How do the tiny AC->USB power supplies work?

texts: The iPhone and Kindle both come with tiny power supplies that take in 120v AC and output around 5V at 0.85 to 1 amp. They seem to be too small and light to have a transformer, and generate very little heat. What is the electrical topology of these little power supplies?


texts: Analog circuit for moving-mean/moving-average

texts:
As a part of signal conditioning stage I am trying to find the moving mean/moving average of a signal at the output of instrumentation amplifier (used LM324-N for instrumentation amplifier).
Is it possible to find the moving average of a signal using analog circuitry alone?
Some constraints -

Signal characteristics -

Frequency range - 0 to 2 Hz
Amplitude dynamic range - 0 to 3.5 V

Window size to calculate the moving average = 5 sec (max)

Preferably op-amp to be used, so as not to overload the output of instrumentation amplifier

If op-amp to be used, it must be single supply (preferably LM324-N)

The signal-

Frequency Range = This is unfiltered signal, but will be band-limited to 0 to 2 Hz
Amplitude is of 10 bit ADC, Reference = 5V
Baseline shifts at approx. = 10/20/30/40/48 sec

Imp. Note - I am using moving average filter for baseline drift correction, and have already achieved in software. The doubt was if this can be done in pure analog circuit alone?


texts: Current source driving capacitor in LTspice

texts:
A circuit is given (see the figure).

simulate this circuit – Schematic created using CircuitLab

where

$$I= \left\{\begin{matrix}
0, & t < 0\\
I_0 sin(\omega t), & t \geqslant 0
\end{matrix}\right.
$$

and the capacitor stores no energy at \$t = 0\$

So, the capacitor voltage can be calculated as

$$V(t) = \frac{1}{C}\int_{\infty}^{t}I(x)dx = -\left. \frac{I_0}{\omega C}cos(\omega t)\right|_0^t$$

This, in particular, gives a DC offset equal to \$\frac{I_0}{\omega C}\$.
Let's the parameters values be: \$I_0 = 1A, C = 1\mu F\$ and \$\omega = 1kHz\$. Then the DC offset should be equal to \$1kV\$. But using LTspice I had just about \$150V\$.
Moreover, this offset goes down with time to the value of \$0\$ (looks like capasitor discharge curve in response to a voltage step in an RC circuit).

Does it mean that LTspice models the components imperfections (internal resistances, for example)? Or my calculations are wrong? If the former is true, how to model ideal behavior?

Thanks


texts: Modify my old (1978) car's existing dash light dimmer (10 ohm Rheostat) to control LED replacement globes

texts:
Firstly my electronics knowledge is limited.

I am trying to work out a way to use the existing Rheostat (10 ohm) that is used to dim the instrument lights in my 1978 car. I have changed the globes to 12V dimmable LEDs, but the voltage drop on the dimmer is not sufficient to dim the LEDs. I have tested the LEDs and they are turned off at about 4.5V and are almost at full brightness at 10V.

I could use a PWM device with a different trimpot, but I would like to use the existing dimmer switch. I thought maybe an Op amp with a 800mA transistor on the output might work, but I am struggling with that concept. Any ideas or available modification circuitry available?

Thanks.


texts: How do I design a PCB for high current applications?

texts:
I'm attempting to design a PCB that will have 8 high-side drivers. I'm struggling with designing the PCB, because it seems the pad on the back of chip isn't large enough to carry the max current it is rated for.

The FET is a VN7020AJTR. According to the data sheet, it's rated for 45 AMP maximum with internal current limiters. According to the PCB trace calculator I'm using, I'd need 32mil (or about .8mm) thick copper on the PCB to handle a trace that's only 2.2mm wide (the input pad on the FET is 2.2x2.9mm).

That's just at the FET. There will multiple FET, and we need to handle up to 100A total (we're limiting in software), I'd need traces 11mm wide.

The 100A limit is easy enough, I can supplement the current capacity by attaching a bus bar, but I still need the traces to handle the current to the pad.

I even considered putting the bus bar on the back side of the board and using multiple vias to transport the current to each pad. I haven't calculated how many vias I would need though. I'm sure it's several.

Now the question, Are my calculations correct? Do I need that much copper just to connect to the FET (assuming a copper bus bar is added) and how do I figure out how many vias I need if the bus bar is on the back side?

If this is anywhere near accurate, it might be better for me to split the FETS onto a separate board than the logic circuits.


texts: Designing a PI controller for my power system

texts:
I have a power system which is given as:

Using MATLAB, I found the system's response to be:

As you can see, the system is not stable.  So, I need to design a PI controller, so that, the transient performance of the \$\ p(s) \$ can be improved.

Therefore, my new system will be:

Please, know that:

\$\ P(s) = C [sI-A]^{-1} B \$
\$\ \Delta  x ' = A \Delta x + B u \$
\$\ Y= C \Delta  x \$

Since we are dealing with a real power plant system, we should consider the input equations to be non-linear. Just for calculation purposes, let us assume that:

\$\ \Delta  x = [\Delta  \delta, \Delta  \omega. \Delta e_q' , \Delta E_d ] ^T \$

Let the angular speed of the rotor ω to be our input. (Just to make everything easier)

Therefor, C= [0 1 0 0]

Where ω can be defined as:

\$ ω' = \frac{1}{M} (P_M - P_E - D(ω-ω_0))\$

Please, know that all of these values are arbitrary, except for ω. (These values will be given to me later by the manufacturer of P(s))

Anyhow, I tried to find \$\ K_I \$ and \$\ K_P \$ using the above equations. So, after using Laplace transforms and many other calculations, I reached to the point where

\$\ H(\lambda)= \frac{\lambda T_W}{1+ \lambda T_W} (K_P + \frac{K_I}{\lambda}) \$

The question is:

What are the best values for \$\ K_I \$ and \$\ K_P\$ so that my power system is stable? And how can I know that?


texts:
I'm not too confident with electronics and I'm currently working on a project where I need a 12V mains power supply. I got a switch for it and have wired it. I've shown pictures.

Is this wiring correct? I'm confident it is, but need someone to check.

Thanks


texts:
I have a solar panel and I would like to use an extension cord. I know this works (heavy duty extension cord) but the guy cut the ends off of the cord to just use the wire (see video links below). I don't want to do that. I would like to add a female socket to the wire ends and plug in the extension cord. I have a few questions about this (I asked at Home Depot and Lowe's and no one had a clue).

My questions:

Will it work?
Will a female plug, say from Lowe's or HD, work with DC power? Everything involved can easily handle the amps.
Could I possibly use a household socket?
Do they make DC female sockets or household sockets?

Edit:

Here's the YouTube video that gave me the idea for the extension cord.

And this YouTube video gave me the idea for the plug. They use a male plug. Does that matter?


texts: How can I "listen" to the activity across a wire?

texts:
First of all, apologies if this is a noobish question; I'm a tinkerer with no engineering background.
I bought a device with two buttons on it. After taking it apart, I saw that these are connected to a small PCB with 5 wires sticking out, which in turn are connected to the main PCB of said device.
I want to find out what exactly is happening inside of those five wires in response to pressing either of the buttons. How can I "listen in" to what happens inside of the wires?


texts: Does gain affect stability of a Transfer Function?

texts:
I have a control system that we are working on with a forward transfer function of:-

\$ \dfrac{K(2s+3)}{s^2(s^4+2s^3+4s^2+2s+7)}\$

So I've set up the routh table for this, I've found there are 2 sign changes, therefore, two poles. But does a value of k=4 affect the control system? Or any value for that matter?

I can't think why multiplying the transfer function by a constant would affect the stability in any way


texts:
I have a system that powers a transformer via a line to line power supply of 115Vac(L-N) for a total of 200Vac(L-L)

In order to control the ON/OFF of the transformer, the NEUTRAL line is used to control a set of MOSFETS triggered off by the Line to Neutral connection. The circuit is as following:

The circuit works well as intended during normal operation for ON/OFF purposes. But if I induce a diode (D7) to one of the phase (L1), the MOSFET attached to it will burn up (M1 in this case). I am using MOSFET IRFBF20S

I have simulated the circuit as I can't run measurements during the induced fault. But all I can think of is that somehow the body diode is conducting or the MOSFET is turning ON but not completly causing the RdsON to be too high.

Ideas?


texts:
Nowadays, There are several kinds of USB connectors for USB connection.

A type
B type
micro-B
mini-B
USB C
Etc.

The connector sizes are gradually smaller than before. It is a big advantage because it reduces board size.

But the B type connector is more suitable for a big size product because it is very easy to connect the plug. But I rarely see the B type connectors now.

Is the B type connector is removed from the standard?
Can I make a product by using the B type connector?

Thank you very much.


texts:
TL;DR - How do I determine the appropriate inductor size to filter out signals at 115.2 kHz? Is the channel frequency determined by the baud rate or the signal rise time?

Edit -10/5/2020

Looks like people want a little more background on design/reqs/idea.
Overall architecture: Master Controller -- Coax Cable -- Sensor
Controller.

Half Duplex comms
8bits @ 1khz. Aiming for 115.2kpbs for overhead and future flexibility
Deliver max 2.5W.
Min 6V @ sensor end

Signal Chain
Master TX port - Inverter - Source Termination - AC couple cap - coax
cable - AC couple cap - rectifier - Inverting Schmitt Trigger - Sensor
RX Port
The goal is to reduce physical footprint at sensor side. AKA minimize
filter inductor size and single supply operation.

Power Chain
Master 12V supply - Signal Blocking Filter - coax cable - Signal
Blocking Filter - Sensor buck converter
From my understanding the signal blocking filter needs to minimize the
energy sent by the signal chain into the power converters. AKA block
most of the high frequency energy.

I've got some more inductors and supplies on the way to do some more experimentation, but insight into the theory would be useful.

End Edit 10/5/2020

I'm working on a project that utilizes a power over coax topology and after running some experiments with various inductor sizes I'm confused how to appropriately size it.
I calculated that in order to have 1kOhm impedance at 115.2kHz I need a 1.38mH inductor. L = impedance / angular_freq
I then tested the circuit by measuring input at C2 and output at C1 through 10 meters of RG178 coax cable. By swapping out various values of L2 (1.5mH, 0.75 mH, 0.5mH, 4.7uH, and  0H) I watched the response at C1.
I didn't see any change between 1.5mH thru 0.5 mH which tells me the inductor is greatly over sized.
I clearly see no signal at 0H (wire) and a slight ripple at 4.7uH which tells me the inductor is too small.
From the oversized scenario I questioned whether my understanding of the channel frequency was incorrect.
Instead should I look at the rise time of the signal? At ~40nsec (25MHz) that results in an inductor value of ~8uH. But that seems too low given my results at 4.7uH.
Thanks for any insight.

0.5mH

0.75mH

4.7uH

Source - https://passive-components.eu/wp-content/uploads/2017/10/Plenary-2-Subrt_Full_Paper_Power-over-Coax-Filter-Design-Challenges-for-Automotive-Vision-Applications_final.pdf


texts: How Estimate Capacity for a Battery If the Temperature is Changing Constantly

texts:
It is the first time I am trying to estimate a battery capacity to can use some devices autonomously.

I found this equation:

Hours autonomy = Battery Capacity x Voltage x Unit x Battery Efficiency / load

for example = 100Ah x 24 V x 1 x 0.8/ 150 W = 12,8 h

But reading from here I saw than the efficiency or capacity of the battery change according to the operation environment temperature.

So, If I will use the battery in a environment where the environment temperature changes a lot until -20 Celsius

How to calculate the correct battery for a load 90W (for example) :

the formule is not valid ?
I need to use integral or complex equations?
I need to do a model of the behavior of the battery in the real place, then make another complex analysis ?
Can I use the worst case of efficiency of battery to use the formule ?


texts: Is it possible to capture a 433MHz RF signal using the PC bluetooth?

texts: I'm student working on a project at my university where I have to transmit a signal that I'm generating with a micro controller using a SmartALPHA RF Transceiver with a 433MHz signal. I have to receive this data and use it to plot a graph on the PC. Is it possible to capture this signal using the bluetooth from the computer? The original project used another SmartALPHA to receive it and transfer to the computer by serial port, but my professor modified it and asked for me to try doing it using only one.


texts: A question about hFE and hfe of a transistor

texts:
I read that hfe is the current amplification factor for small signals. And hFE is the current amplification factor for DC signals.

Does that mean hFE should be used when biasing and hfe should be used for the AC analysis? Or is in practice one of them is used? It seems hfe and hFE are quite close(?). Which one matters more in practice fx. to read in a datasheet?


texts: overloading rated current capability of a connector

texts: If each connetion of a screw terminal (the one in question in the picture) is rated for 3A at 380V, is it probably safe to use each one for 12A at 12V? Is there a way to work this out? Thanks


texts: Not understanding Forward Voltage and Voltage Drop

texts:
I have a simple circuit:
+12V -- R1 -- LED1 -- LED2 -- LED3 -- ground
Falstad simulation link
If the Forward Voltage of an LED is 3V, and the Forward Current is 20mA, I can (I believe) calculate the required resistance of the resistor as (12V - (3 * 3V)) / 0.02A = 150Ω.
From what I understand, that should give me a Voltage Drop of 3V over the resistor and each LED respectively, and a current of 20mA through the circuit - perfect.
In the simulation of this circuit, I get a Voltage Drop of 4.01V, 2.66V, 2.66V, 2.66V respectively, and a current of 26.74mA through the circuit, which is too high for the LEDs.
This makes me think that I don't understand the relationship between Forward Voltage and Voltage Drop, and therefore, how am I supposed to calculate a correct resistor value that won't burn out the LEDs?
Apologies if this is asked a lot or is really simple, but I've been searching for ages and haven't come up with anything.


texts: Powering an Arduino Pro Mini 5V and a 3.3V nRF24L01+ Transceiver from One Small Battery

texts:
I'm trying to power an Arduino Pro Mini 328 5V/16MHz with a single battery, preferably a LiFePO4 for safety purposes (it doesn't need to be more than around 300 mAh). However, I'm connecting a transceiver to the Arduino, and it requires 3.3V. This is the transceiver I'm using:

http://www.addicore.com/2pcs-Addicore-nRF24L01-Wireless-Transceiver-p/112.htm

This is the Arduino Pro Mini I'm using:

https://www.sparkfun.com/products/11113

My thoughts were to get maybe a 2S LiFePO4 battery, with nominal voltage at 6.4V, then use a linear voltage regulator to bring that 6.4V down to 5V to power the Arduino, then use another linear voltage regulator to bring the 5V down to 3.3V to power the transceiver. I fear that this may cause some damage somehow, as I'm not too experienced with voltage regulation. Will too much heat be produced? Is there a simpler way?

Any help would be greatly appreciated. Thank you!


texts: Can wire gauge be increased gradually over the length to compensate for voltage drop?

texts:
Assume DC. For a given amperage and distance, does the wire gauge need to be constant over the length of the cable?

For example, assume 3% acceptable voltage loss, 24Vdc, 10 meter, 50 amp. A cable gauge of 2 AWG would be needed to stay within the acceptable voltage drop.

However, over a 1 meter cable, 10 AWG is enough.

If the cable length is 10 meter, could the first meter be 10 AWG, and the remaining 9 meter 2 AWG? Similarly, does the required AWG change gradually as the distance increases?

This calculator was used to arrive at the required AWG: https://www.solar-wind.co.uk/info/dc-cable-wire-sizing-tool-low-voltage-drop-calculator


texts:
I bought a trrs audio jack breakout and i tried to use this using arduino. I connected the tip to an analog output (I made a pwm to analog converter), I created program on arduino that send 10% voltage in the pwm and  I heared a sound but it didn't changed when i changed the voltage(for 10% to 9%, 11% etc). I have two questions:

Is there any voltage limit in the trrs audio jack?
How can i actually change the sound of what I hear in my headphones (change the sound frequency the sound)

Edit: You told me to change the PWM frequency and I did so and the sound did change, then I used my raspberry pi and I changed the PWM frequency to some values (between 20000-20 hz) and the sound chaged. My problem is that my arduino does not supert changing the PWM frequency freely (I cant change it to any frequency I want). My raspberry pi does support it but I want my project to be portable (I have arduino nano). How can I solve this problem? Is there any PWM chip/module?

Thanks.


texts: 2 outputs of same op amp gives different voltages

texts: I am using lm358p op-amp for 2 different heaters I connected both of them in a single op-amp and it didn't work firstly I thought that the problem was thermocouples I swapped them but the problem kept going then I made the connections in a breadboard when I used the first amplifier it worked just fine and then I swapped the amplifiers and 2nd amplifier gave a different value (note: I didn't change anything else and I tried with a 2.0v power supply too) I changed the resistors the capacitors checked all of them but it still doesn't works could you help me here is my schematic


texts:
I'm trying to jump in the USB world with LUFA on a Teensy dev board, but I'm stuck in the understanding of the descriptors.

Currently I'm trying to add one button to the joystick demo without sucess. Does anyone know some resource that explains step by step how to set up a USB descriptor?

edti :
After reading USB in a nutshel, I think I may not modified the Descriptor at all but the HIDReport instead...


texts: Writing the bootloader program into ATmega32A

texts: I am in a need of programming a bootloader code written in C into the boot section of AVR ATmega32A using a serial programmer. I can't write the code directly into the boot section from Atmel studio. So, I am looking for a way here. Also, is there any good way of combining application code and Boot code and write them in respective sections using C program?


texts: I am trying to read load cells data, but these values are very fluctuating. I have ADS1230 ADC and I had configured it to the internal gain of 128. Four half-bridge load cells are connected in a bridge configuration and the output of bridge is fed into ADC. BUt there is no way i can get stable reading. It would be great to know what i am missing here. Would EMI be the Cause here? Any suggestion would be appreciated.


texts:
I'm trying to know the fr equation for the following op amp configuration:

I have some capacitors values for specific fr frequencies:

fr = 34Hz -> C = 33nF

fr = 50Hz -> C = 22nF

fr = 160Hz -> C = 6.8nF

fr = 330Hz -> C = 3.3nF

fr = 1.1kHz -> C = 1nF

fr = 2.3kHz -> C = 470pF

fr = 6kHz -> C = 180pF

fr = 16kHz -> C = 33nF

Capacitors are not exact values, they are commercial. I know these values are correct because I saw the frequency response in an oscilloscope.

I was searching on web and found this:

This is the page where I found it: https://www.electronics-tutorials.ws/filter/filter_7.html
The circuits are very similar. The difference is R9 resistor which add an offset to the input signal. This offset is to use just one power source instead of two.
The page give me an equation to calculate the fr frequency.

But when I replace the values in the equation, it doesn't give a close values as the practical capacitance.

fr = 15.25Hz -> C = 33nF

fr = 22.87Hz -> C = 22nF

fr = 74.01Hz -> C = 6.8nF

If I multiply the equation by 2, it give me a closer value.

fr = 30.5Hz -> C = 33nF

fr = 45.74Hz -> C = 22nF

fr = 148.02Hz -> C = 6.8nF

If it is the solution, I would like to understand why.

If someone could explain me the first op amp configuration, I would be very grateful.


texts: How to calculate this current limit circuit?

texts:
How to calculate this current limit circuit

This is a current limit, can anybody give me some instructions about how to calculate the limited current?

My calculation is as follows:

(V1-0.51*I)*33/(33+3)=V1-Vbe

V1=5V,Vbe=0.6V

thus Ilimit=392.2mA

It seems right as the simulation in pic1, but when I change the Input voltage of V1, the current limitation seems changes as another simulation(pic2)

  In pic2, a different input voltage of V1 makes different current limitation.

V1=4.03V I=409.8mA
V1=5V I=331.38mA

Can someone give some formula about how to calculate the current limitation vs different voltage input?

simulate this circuit – Schematic created using CircuitLab

  question update:

I have searched many other similar questions in the StackExchange. Interesting is  I found a very similar schematic as follow:

simulate this circuit

This schematic is coming from Jonk's another answer

How can I calculate knee current for this foldback current limiter

Now I will ask what's the difference between these two schematics?

First I can see is the R4 resistor, the biggest difference is one of the R4 is connected to GND and the other is connected to Rload?
And which schematic seems better or uses more frequently?
What are the advantages and disadvantages of the two schematics?


texts: Strategies for powering an ATtiny micro controller and 40W peltier from mains

texts:
I'm trying to power an ATtiny1634 at 5VDC and a 50W peltier element at 12VDC. The microcontroller will, amongst other things, turn on the peltier via a 5VDC non-latching relay. I want to use an embedded SMPS that will convert mains power to DC suitable for powering the aforementioned two devices. Also, I would prefer all components except the peltier to be PCB mounted as the components need to fit within a tight space.

What different approaches are there to powering these devices?
In terms of simplicity I'm leaning towards a simple 5VDC 1W SMPS to power the micro controller and a 12VDC 40W SMPS for the peltier. The problem I have with this approach is that it becomes prohibitively expensive to put together. For PCB mounted power supplies in the 40W range, manufacturers like Tracopower charge ~USD 95, add in the 5VDC SMPS and that's over USD 100 just to power the devices.

Would using the 40W SMPS to power both sub-circuits be a viable option? If so, how?

It is still expensive to spend the USD 95 for the 40W SMSPS but it is an option if push comes to shove.


texts:
Only interested in the binary logic part, not the motor side. The datasheet specifies a few absolute max ratings:

  Table 4. Absolute maximum rating

  IIN Input current (INA and INB pins)  +/- 10  mA

  IEN Enable input current (DIAGA/ENA and DIAGB/ENB pins)   +/- 10  mA

  Ipw PWM input current     +/- 10  mA

  ICP CP output current     +/- 10  mA

  ICS_DIS CS_DIS input current  +/- 10  mA

and this ON-state supply current:

  INA or INB = 5 V, PWM = 20 kHz      8  mA

According to this answer i need to worry about the sank / sourced currents as well as the quiescent current. If this is the case, then how would I identify those currents for my specific part ? Is there a generic rule for any IC ?

edit

I was not clear on this one. What I am looking to do here is to sum up all the currents in my circuit so I can size a voltage regulator for it.

edit

the specs were actually right there in another table, I was just searching for 'mA' instead of 'μA'. Seems these "CMOS compatible" IO pins are very amp-efficient:

  IINL Low-level input current VIN = 0.9 V               1 μA

  IINH High-level input current VIN = 2.1 V             10 μA


texts: Power calculation in kwh over a period of time with a variable current source

texts:
I have an experiment running which generates variable current due to a chemical reaction over a period of 8 hours. I sampled the current at each hour with a constant voltage supply of 12V. When i use P= I*V i get the power at that particular reading.

My assumption to calculate a the power consumed during the complete experiment was to plot a graph between the power at each hour and experiment duration. Calculating the area under the plot graph will be power calculated per experiment but not in kwh.

Is my assumption true or is there a mathematical formula that i have to use to calculate the power in kwh.


texts:
What acquisition mode should be used on the oscilloscope ? I have a GW Instek GDS-1052-U. I can choose between Normal, Average and Peak Detect. Which is the best ?
Also, when I am using Average I can select a number from 2 to 256. If I select 256, the trace is at first very noisy and it getting less noisy in a few seconds:
Average 256, when I connect the probe to the LM317 power supply:
https://imgur.com/a/LE8ZF
Average 256, after about 10 seconds:
https://imgur.com/a/MWcZr
Average 256, after about another 10 seconds:
https://imgur.com/a/QfPwn

It is normal for the trace to be more noisy at the moment when I connect it to the signal source and after a few seconds to get less noisy ?


texts: Why can't the two plates of a capacitor have unequal charge?

texts:
This is what was given in my textbook:

"The net charge on every component in the system is always zero. Thus no component can collect a net excess of charge, although some components can hold equal but opposite separated charges."

I can't quite understand why this is so. For example, what would happen if the two plates of a capacitor had unequal opposite charges?


texts: Mysterious energy disappearance of capacitors

texts:
Consider a capacitor,
$$ C= \frac{Q}{V}$$
To derive the energy of this device,
$$ U = \int V \cdot dq$$
$$ U = \int \frac{Q}{C} \cdot dq$$ (from original capacitor equation)
$$ U = \frac{Q^2}{2C}$$
Plugging back in, $$ C = \frac{Q}{V}$$
$$ U = \frac{ QV}{2}$$
Now if a 'q' charge is pushed out the battery, then it must do work $$qV ,$$ so I was thinking this same energy would be given to the capacitor but only half is. Where did rest of the half go?
And, my next question is why is the potential not constant across capacitor? That is why can't we factor out the 'V' from the integral? Because according to the Kirchoff voltage law, the sum of voltage drops across a closed loop should be 0. Below I have attached a picture of a circuit with capacitor and battery, for it shouldn't the energy be
$$ V_{capacitor} + V_{battery}=0$$
$$ V_{capacitor} = - V_{battery}$$
usually we say that the potential of battery is constant, if the potential of battery is constant wouldn't this imply potential of capacitor is constant?

Ok, so suppose the actual voltage is changing in the capacitor as increase the charge on it, then what happens we reach the maximum charge on it and still have it plugged into the battery? Would the capacitor become defective?
Edit: A lot of people gave an answer that there is an aspect of inductance in this idealized circuit and also the release of electromagnetic radiation. I am now looking for a mathematical description of the inductance aspect of this radiation and also a proof of energy lost to radiation being  .5 CV by application of Maxwell law's. I mean if it is indeed true then we must be able to bring out by Maxwell law's, right?
References:
Same problem is said here Why do I get the wrong answer when determining the charge in a capacitor using definition of voltage?
but no explanation as to where exactly the half is coming from.
Edit:
What exactly is wrong in this derivation for k.v.l ( The Feynman Lectures on Physics, Volume II, Chapter 22: AC Circuits)
$$ \nabla  \times E = \frac{ -\partial B}{\partial t} = 0$$ (maxwell faraday eqn)
Integrating over any loop in the region,
$$ \sum V_i = \int E \cdot dl = \int_{\partial S} \nabla \times E \cdot dS=0$$
i.e:
$$ \sum V_i = 0 $$
Which step is causing problems to have the seeming violation of kvl for the problem stated?


texts: How to make a togglable switch using a signal?

texts: So I'm working on a science fair project and I need help with part of it.  I'm using a pressure sensor, and I want to use the output of that as a toggle switch to allow power to something else.  I'm taking the output of the pressure sensor, and I need help making it so when there is output on the pressure sensor, then the switch is open, and if there is no output, then it's closed.


texts: is there any software working on PC with a gui that can control the outputs and read the inputs of an arduino in realtime?


texts: How is it possible to produce picovolts or femtovolts? (artificially)


texts:
I am currently having an issue with precision control of small brushed DC gearmotors (130 size) being used as drive motors on an autonomous robot, but this question can be applied to small, high-speed DC motors in general. On my robot, I am driving the motors with an L293D-based dual H-bridge controller, controlled by a microprocessor. I have found that simply setting both of the microcontroller outputs connected to the H-bridge low will not stop the motor quickly enough for the robot to immediately stop, resulting in imprecise turning, even when running the motors at the lowest speed possible without stalling.

I decided to try an experiment with braking several DC motors (RF300, RF370, and 130 size) with and without a 2.5-ounce flywheel on the output shaft. I connected both of the motors to 5 volt power, allowed them to reach full speed, and then disconnected power and shorted the leads on each motor using a DPDT switch, and compared the time it took for them to stop with and without shorting the leads. It seems that the stopping times for the motors are relatively the same whether or not the leads are shorted. The motors with the flywheel attached took longer to come to a stop, as expected. The same results were obtained by running the motors at 12 volts.

Is it actually possible to brake small motors?


texts:
I'm working on a sprinkler/lighting controller project where I need to supply solenoids with 24VAC and lighting fixtures with 12VAC. I can use a different circuit for each. The input to the system is about 22V (a square wave rectified through a diode bridge rectifier) and may be lower depending on losses from resistance in the (long) transmission wire. Lowest voltage at the end of the wire will be 14V, with ripple of +/-2V.
I'm looking for the cheapest solution to create 24VAC and 12VAC from the 22VDC supply I have. I have already tried using an H-bridge to generate a sine wave approximation with a microcontroller, but the huge filter required to get an acceptable sine wave out (at least according to LTSpice simulations) is huge and the BOM cost is too high. Typically my loads are at about an amp or less, but the current spikes in the simulations are 2x-3x times that.
Are there other solutions that I'm overlooking that might be able to generate a clean(ish) sine wave? If this is indeed the cheapest way, how can I reduce the current spikes to decrease the needed inductor size? What is considered clean enough when it comes to generating AC?
And no, I can't run the solenoids/lights off 12VDC. Don't ask.
Here's the current H-bridge circuit in question

And the 34V boost regulator I'm using to power it.

Edit: Here's the repository for the simulation: https://github.com/davidcutting42/sprinkler-simulation


texts: designing a 3-bit comparator using only multiplexers

texts:
I need to design a 3 bit comparator using only multiplexers specifically 74ls153 and/or 74ls151. I've already constructed the truth table(see below) and realized that A=B is not needed since its inferred when both A > B & A < B are equal. My thought process has me using three 74ls153's to compare pairs of bits starting with the LSB and working my way up to MSB. One "side" of the mux is wired to output A>B and the other "side" wired for B>A.

I am

a) unsure how to carry these outputs to the next multiplexer / final multiplexer

b) how to convert this to a 2-bit output

I'm not looking for an outright answer, more so a point in the right direction with a better understanding.


texts:
I'm trying to make my own board for a CC1101 transceiver that will operate at 915 MHz. To do that, I'm just copying the reference design layout from the eZ430-Chronos-915 RF Access Point that uses a CC1101 with a MCU to be used as a dongle. This is the reference design PCB, I could only find it in PDF format as an image:

(Inside the black square are the 0.25 mm tracks and inside the red square is the 0.4 mm track)

And this is the schematic section corresponding to the CC1101:

By measuring the image I got that the tracks coming out from the RF_N and RF_P pins are 0.25 mm wide, this is on a two-layer FR4 board with a thickness of 0.8mm, so that will be around 100 Ohm impedance for the tracks which is right because it's a differential signal AFAIK (to maintain 50 Ohm impedance, correct me if I'm wrong please).

These two tracks go to a Balun (this one) and the antenna connection is made on pin 1 of the balun. This is the typical layout:

The balun says the impedance of the track going to pin 1 must be 50 Ohms. I measured that the track that goes out from pin 1 is 0.4 mm wide, with a two-layer, FR4 board with a thickness of 0.8 mm that is an impedance of around 88 Ohms, not even close to 50 Ohms! To get a 50 Ohm impedance the track should be 1.5 mm wide.

What am I missing? I know this design works because I have this board and it works as expected. I was planning to put a 50 Ohm SMA connector in the end, should it then be 50 Ohm or something closer to 88 Ohm?

All the pictures are taken from here.


texts:
I am working with a PIC18F67K22 and am seeing some bizarre things in the SPI data stream. I am trying to interact with a FAT32 partition using FatFs and a custom built diskio.c file. I am able to recognize the FAT32 partition, but when attempting to create a file, the disk_read operation suddenly gives weird errors.

I have attached a screenshot of the logic between the PIC18 and the SD card to show the unusual data.

In the screenshot, you can see that I am sending CMD17 (READ_SINGLE_BLOCK) along with a 4 byte address of 0x00007D10 and a CRC7 checksum for that command.

The command response that I receive is 0xC1, followed by 0x3F, neither of which make any sense. According to the How to Use MMC/SDC section on the FatFs website, the command response's most significant bit should always be a 0, but 0xC1 has the most significant bit set to 1. In addition, why is the 0x3F coming after? That should be 0xFF.

And even if I assumed there was a bit shift here and the actual value should be 0xC13F >> 6 (0x04), that would be an illegal command. What is illegal about CMD17 with that address? Is the data address of 0x00007D10 invalid? The partition should span the entire media, except for the MBR and boot record.

Edit:

Here are the sectors returned during initialization, with some annotations on the data:

Master boot record
Partition 1 boot record

Edit 2:

I've discovered this only happens if I call f_mount well before f_open. I am doing an f_mount upon insertion of the SD card to verify that the card is a proper FAT16/FAT32 partition, and then only calling f_open when the user begins to record data. If I call f_mount and f_open in rapid succession (or call f_mount with delayed mounting), then the call works fine and the command returns 0x00 and then 512 bytes of data.


texts: I want to to my RaspBerry Pi 4 with an old small CPU fan. However it's a 12V fan. Is it possible to use 2 of the 5V pins on the board to total to 10V? Sorry if this is a dumb question. I haven't worked with electronics in a while.


texts: Is 763uOhms @603kHz considered to be bad (very low) when it comes to output impedance. Would it be a dead short? My design for a Buck Converter shows this as its output impedance. How low is ok ?


texts:
I'm working on a project that is clearly showing me that power electronics is a completely different beast.
We have a 5HP motor running on a 120Vdc battery. The motor is installed about 100ft (30m), away with big cables. At the moment the motor turns on it peaks at about 180A, then is rests at about 44A. I'm looking for a way to limit the startup peak at about 70A.
Following my first idea, I've chosen a 150A IGBT and a magnetic loop current sensor, like this:

Close to the motor, I have a high current freewheeling diode, and on the IGBT I have a RCD snubber with 1uF capacitance (seems small to me but here, I see that the rule of thumb is 1uF per 100A...).
My control is simply to turn on until the current sensor rises to a top limit then turn it off for a fixed amount of time and repeat... At some point it will work on forever without tripping the top limit. The motor should remain on for only a few seconds and then go off, so things should not get too hot, hopefully.
While projecting and layout-ing the board for this "simple" project I've realized that a lot of things can go wrong.
Does someone see something I'm missing? I do not have boards yet, so never tested the circuit, but, after seeing a lot of people having problems with IGBT dealing with much smaller currents I am already thinking that I should stop and study more before going ahead with this approach.
Another new idea is to turn on the motor with a high power resistor in series to limit the current for a few mili-seconds and then short the resistor with an SCR. But I feel I'm simply changing monster's name (is an SCR simpler to tame than an IGBT? I don't know...)
Also found the CS8312, IC. Maybe replace its serie resistor current sensor by my loop current sensor?
And, no! I'm not asking for a ready solution, just like to hear a more experienced opinion on what I should study to have a reliable solution.


texts:
I am making an audio amplifier using an LM2879. I am using the schematic provided in the data sheet.

For a starting point, this design works pretty well, although the base cutoff point could be a bit lower. When I power this circuit on, I am greeted by quiet, high pitched static regardless of the volume of my device. When I play music, the quality of the music is good. I believe the static is coming from my power adapter because someone else in the reviews for this product said it was electrically noisy. Is there a way to filter out this noise at all? If you have any other ideas of where the static is coming from, I would appreciate the help.

Thank you!


texts: How many cycles does an ARM Cortex M0 use to multiply floats?

texts:
On an ARM cortex m0+:

How many cycles does it take to perform multiplication of single precision floats and store them into a float? i.e. x = a*b; Where x, a, and b are single precision IEEE 754 float point... and what if they were both double precision?

Bonus Question:
How many cycles does it take to shift an integer by 16 bits and store it into another integer. i.e. x = (y>>16); Where x and y are 32-bit signed integers.

EDIT:

Compiler I will be using is the ARM gcc compiler

The reason I ask this question, is I plan on using q31, but I wanted to see what the difference really would be


texts: How does an optical (toslink) to HDMI cable/converter work?

texts:
I'm looking at the small Sonos optical audio (toslink) -> HDMI cable in front of me and I don't know how it works (https://www.sonos.com/en/shop/optical-audio-adaptor.html). It has an optical audio input and can be connected to a speaker via HDMI, so basically it looks like it converts the optical signal.

I can only find clunky HDMI audio splitters that also output optical, but I don't know how this cable works since it is so small - or is it and this is totally normal?

How do optical -> HDMI cables / splitter work anyways? Is there a small IR diode in there detecting optical signals directly converting them? Is there a small contraption inside this cable?


texts: OBDII Which hardware and software allows scripting via unix terminal

texts:
I developed an embedded design with dsPIC processor, which is a remote start module, communicating via 6 CAN busses.

Often I would need a much quicker, simpler solution to test something on CAN bus, without writing compilable program.

I need an Unix terminal scripting capability, plus a compatible hardware OBD interface (USB or wireless), one CAN channel suffice, more is better.

Anybody can recommend such a combination?


texts:
I was in a training class and the instructor went quickly over how to use a single output momentary switch to effectively drive 4 different states, which he didn't think was important and skimmed--so that on each push (assuming you're starting with all inputs low) you get something like
1000, 0100,0010,0001, and then start over. I took a snapshot (below) of the screen that we were using, but I'm a bit confused as to the route we took using the flip flops and logic gates. His also seemed a buggy, so i'm wondering if using AND/OR/NOT and flip flops if there is a more efficient way to do this?

1) Is this technically a binary counter
2) Its not clear how to break think about this, as his way seemed super convoluted and didn't always work correctly, particularly at resetting the 4th state to the first.


texts: How can I multiply (double) my input frequency without distorting my waveform?

texts:
I'm looking to double my input frequency in my circuit, but it's important that the signal stays the same shape as much as possible. I'm working with low sine wave frequency's.

Edit: Sorry it took so long to get back. I am working with audio signals.


texts:
I have this circuit on a board:

That circuit is supposed to act as a push pull amplifier working as the following:

In case it is not really visible the voltage connected to the collector of Q3 is 3.3V.
Debug signal is connected to the output pin of a microcontroller and change from 0 to 3.3V.
A red Led is connected between J3-1 and J3-2
A green Led is connected between J4-1 and J4-2.
When Debug is high the green LED is supposed to turn ON and the RED
LED off.
When debug is low the red LED is supposed to be ON and the green OFF.

The circuit works.

What I do not understand is, how it actually works, when I look at it it seems to me that :

when Debug is high, the base-emitter diode of Q3 become active and
the current actually flows from the output of the microcontroller
directly to the green LED through the base-emitter diode.
On the other hand when Debug is low the emitter-base diode of Q4 is
active and the currently flows directly to the pin of the
microcontroller through the red LED.

Then there is no amplification of the current at all.
If it is really what's happening it only works because the LED current is smaller than the max output current of the microcontroller and this arrangement is actually not amplifying anything?

What should be happening is when debug is high Q3 become saturated and current flows from the 3.3V to the green LED. When debug is low Q4 should be saturated and curent should flow directly to the GND.
Am I right thinknig this is not what is happening? And if Q3 and Q4 actually get saturated, how does that circuit works because I don't get it.


texts:
I have a multimeter which does not include capacitor checking facility. So, the method I am doing to check capacitor is, that, first I connect it with a battery for some seconds and check the voltage across the capacitor. If the votage is same as the emf of battery, then I conclude that the capacitor is working. But my friend says that this is not a suitable method, as the voltage is not same as capacitance. But I argue that this only the test for working of capacitor, and if it works properly, then the capacitance should be equal to the quantity that labelled on it. But he disagree me without reason.

Is my method is wrong? Then how I detect failure of capacitors?


texts: Is there any way to acquire -12 V from +12 V?

texts:
Is there any way to get -12 V (DC) using only:

+12 V DC
Ground
OPAMPs
Resistors
Capacitors
Inductors
Diodes


texts: My Buck-Boost Converter Circuit Isn't Working

texts:
I am currently working on a heated glove project using a Buck-Boost converter to adjust the temperature of the glove. I'm using the LTC3112EDHD#TRPBF QFN Buck-Boost IC to control the Buck-Boost functionality. I just finished soldering my test PCB, and my Buck-Boost Converter IC isn't outputting a voltage. My multi-meter is reading a voltage output of 0V. I've included my schematic design below. The PCB layout is exactly the same as the schematic. Some of the ports on the IC are controlled by a micro-controller.

I honestly do not know what could be the issue with this circuit. My two guesses are that either some of the passive components got damaged during soldering (which I doubt. I confirm the resistors work properly, but can not confirm the capacitors functionality due to my multi-meters limitations), the Buck-Boost IC isn't solder correctly, or my design layout is incorrect. Any help would be greatly appreciated.

Edit: I've added the PCB layout of the schematic. It may be hard to see due to all of the connections, but I've included it as a reference.


texts: Does a BJT amplify the biased DC voltage or just the AC/DC input voltage?

texts:
From http://www.electronics-tutorials.ws/amplifier/amp_2.html, i understand that the voltage gain of a common emitter BJT is given by below equation; where RL is the load resistance, RE is the resistance between emitter and ground and Re is an inherent BJT emitter resistance.

This voltage gain is applicable for both AC/DC input voltage. How about the biased DC voltage? Does it get amplified as well?

Basically i would like to know whether a BJT (common-emitter example) also amplifies the biased voltage (applied at the base). In the absence of any input voltage, can i say that the output voltage (at the emitter) is equal to biased voltage (0.7V for example) multiplied by the voltage gain [-RL/(RE + Re)]?

Thank you.


texts: LC tank circuit feeding on op-amp, no oscillation?

texts:
Based on what I learned during this experiment I've built the following circuit using an op-amp configured as a buffer...

simulate this circuit – Schematic created using CircuitLab

The inductance of the coil is unknown. I have found no way to measure the inductance of the coil on my oscilliscope in Henrys without some form of a wave generator...which I don't have.

My multi-meter registers .1v-.2v on the capacitor, and .1v on the coil. It remains constant.

Shouldn't I be getting some form of oscillation in voltage when probing either the coil or the capacitor? From my understanding I'm creating an LC-Tank Circuit and supplying the current the Tank Circuit needs to continue stable oscillation which it lost due to resistance.


texts: How can I deduce the power of a capacitor from its datasheet?

texts:
I am looking for suitable capacitors for a sound amplifier I have designed.
The speaker power should be at least 7 watt (for the sound to be loud enough).
(I attach a figure of the design)

So, I think I need capacitors which are suitable for these level of power.

But, in the datasheets, i don't see any specification for the power capability of the capacitors..

Any idea how can I know I have chosen capacitors with high enough power resum capabilities?

Thanks!


texts: Why does the "top" transistor in a cascode not set the current?

texts:
This has been bothering me for some time. Why is it that the overdrive voltage of the bottom transistor in a cascode controls the DC current, and not the Vgs of the top transistor? Similarly, in an NMOS diff pair with a current mirror on the bottom, why does the overdrive voltage of the mirror control the current, and not the common-mode voltage of the pair?

This came to mind when I read in a textbook that it is improper to draw a current source feeding the drain of a transistor, rather than pulling current from the source.


texts:
I have asked the question here and someone offered to ask here in order to get better answers, so here it is:

  History:

  I decided to design a circuit with some peripheral ic's. Although SPI
  may achieve great data rates, because of its master-slave architecture
  and separate chip select pin requirement, I decided to use I2C because
  of its multi-master and real serial design. (SPI is not a fully serial
  protocol, it's more like a hybrid protocol: serial port for data
  exchange, parallel port for chip select lines)

  Problem:

  I've been planning to add some adc, dac, gpio ic's to a
  microcontroller but these modules are produced with a few slave
  addresses available. Manufacturers are embedding slave's addresses
  into the ic hardware. What a bad idea! So, I have faced with the
  addressing problem of i2c protocol.

  Some of the ic's present address assignment pins (3 pins, which means
  I would not use more than 7 of them). That's not enough in my case.

  Some people offer scanning addresses from 0x00 to 0xff, but this is
  not a good approach because it's time wasting (I think). Someone says
  "There are  i2c buffer's or i2c MUX's you may use" or even another
  microcontroller for address translation (NAT like approach) but
  weren't we choosing and using i2c for simplicity (like fewer routes on
  board, flexibility etc) in the first place?

  There are people having this address assignment problem (eg.
  http://www.linkedin.com/groups/Methods-enumerating-I2C-slaves-autoassigning-4023060.S.113408032)

  Suggestion:

  Automatic address assignment could be done with an algorithm something
  like that:

  Slave components would have 2 bytes of non-volatile memory in order to keep their addresses permanently.
  Slaves will have a default address (eg. 0x01).
  On power up, if slave has not been assigned with an address different from default, slaves will become master and ask for an
  address from the host (eg at address 0x00).
  Our actual master node (microcontroller, the host) (in this example which has "0x00" address) will act as a slave naturally, because there
  is another master on the bus and will respond (assign) next available
  address to the slave.
  0x01 address will be reserved for broadcasting. Master may use this address in order to make slaves reset their assigned addresses.

  That would be enough for automatic address assignment.

  Yes, I know about SMbus. It has automatic address resolution protocol,
  but it has other limitations (speed, timeout etc) which makes me not
  want to prefer SMbus over I2C.

  This address assignment protocol may be optional and could be
  activated by a single pin on the ic package. So, it will be backwards
  compatible.

  Question:

  Probably I'm not the smartest person in the universe but,

  is there an address assignment protocol that vendors already implement in i2c
  if not, what would be wrong with this protocol
  if nothing is wrong, why don't they possibly start implementing a protocol like this (again, I know I'm not the smartest person, so they
  should have taught about this problem and they should have already
  discovered an algorithm like this)


texts: Using a Renesas evaluation board as a Programmer

texts:
I am new to using renesas microcontrollers, and could use some advice from someone with experience using them. I found this rl78 evaluation board and a quick reading of the product description on the renesas website mentions that "It has a built-in emulator circuit that is equivalent to an E2 emulator Lite so you can write/debug programs without additional tools".
My question is, once i begin prototyping on the controller existing on the board, is it possible for me to use this evaluation board as a programmer to flash code to renesas rl78 controllers on other PCBs and use the same debugging/emulation features? Or would i have to get an E2 Lite programmer which is way more expensive?
If i can use it as a programmer, i could use some pointers on how i could do that. Any help would be greatly appreciated.
Thank you.


texts: How do you calculate the peak current of an electric motor?

texts: I'm designing a BLDC motor and have a required constant load torque to figure out the winding size required, but I also want to know what peak torque/current it can output for a few seconds. What is the limiting factor of peak current?


texts: Eagle/Flatcam/LaserCNC: How to have "open pad" for futur drilling

texts:
I'm using Eagle, flatcam and a CNC laser machine.
My problem is when I'm trying to export my board, all my pads are filled !
It means, when my board will be engraved (chimical method), I will not find any holes in the middle of the pad to use for drilling (manual)

Eagle board:

Flatcam preview:

Do you know where I can change this to have "open pads" ?
It's an eagle parameter ? flatcam parameter ?

Thanks for your advice, I'm a newbee


texts:
I'm designing a board with some MOSFETs that dissipate a fair amount of power.  The best device (low Rds and low Qg) available in this scenario would run at 30W max.  This is available in D2PAK and TO-220.

What is the preferred option for cooling D2PAK at those power levels?  Some of the options:

SMD stamped heatsinks on the drain pad, straddling the device (like these goofy things).  Aavid 7109D resistance from mounting surface to air is 2.75C/W at 400fpm and 2C/W at 800fpm, this seems marginal in this case (since the connection between heatsink and device is thin copper conducting sideways).
thermal vias under device and a big heatsink epoxied to the board on the other side (one per device, not isolated)
thermal vias under device and a big aluminum plate heatsink on the back of the whole board (isolated with a pad)
aluminum core pcb or extreme thickness copper pcb.  I'm guessing this makes the boards significantly more expensive, and prototyping more difficult.  A metal core board would still need to connect to a heatsink somewhere, or the board would have to be extra big to give it enough heatsinking ability.
multiple devices to reduce dissipation per device.  this almost seems cheaper than a complex cooling solution.
give up on using SMD and use TO-220 where <1C/W is fairly easy :)  some concern about manufacturability in this case.


texts: Looking for N-Channel MOSFET with igss<10nA

texts:
I'm looking for a surface mount mosfet with a gate leakage in the pA or very low nA range, so I can drive the gate from a very high impedance source.  Since most people don't care that much about igss of a mosfet, it's not a searchable parameter on Digikey, Mouser, etc.

I have found some mosfets with igss in the pA range, but they seem to be out of production.
However, that proves they can be made.  I was hoping somebody could point me towards a part.


texts:
I want to get 1.8v to power a gps unit, from the 5 volt pin of an Arduino.

What do I need to change on this schematic to achieve that voltage?


texts:
Can a 4-switch buck-boost be reversible?

The base scheme seems symmetrical but I did not find any reversible design.
Do you have an exemple of such a design?


texts: Do we ever bypass the noisy component rather than the control ICs?

texts:
We should always bypass the power to ICs in our projects, and there are many related questions here.

Are there times when we should instead (or as well as) bypass the device that creates the noise in the first place?  Switching say 10A causes significant spikes or drops.  Examples would be  power relays, motors or even a high power LED that's controlled via PWM. So we would have capacitors directly across the relay contacts or across the FET switching the LED. I don't see this done often, instead focus seems to be on the control circuitry.

One issue I foresee is the size of the capacitors.  We typically stick 0.1uF to 1uF capacitors across most common ICs, perhaps going as low as 10nF for high speed ones.  This has been well discussed.  It seems to me that it might be more difficult to assess what size to use for power devices...

So to be clear, I'm not asking about bypassing ICs but rather the large metal thing they might be causing to switch on and off.


texts: Why are automotive connectors and wires so big?

texts:
Cars and motorcycles have many electronic sensors which are small. But it seems they are all connected with big connectors and at least 22AWG wires. Why?

I would think 30AWG wires and tiny connectors should do the job because there is very little current going through those wires.

Or is the idea that car and bike mechanics maybe wear gloves and work with lots of force so the developers makes the wires and connectors big so nothing gets easily destroyed?

Any idea? There must be a logical reason for this.


texts:
I want to build an amplifier. I got a circuit diagram from a website, Amplificador Monofónico de 250 Vatios Cuasicomplementario.

I want to know the class of this amplifier.


texts: LED driver type detection- 0-10V or DALI

texts:
I am looking for the solution which can automatically detect the driver type installed in street light luminary.
There are control mechanism which controls and provides the 0-10V and DALI dimming to driver installed in luminary.
Now what I want is I to develop mechanism that automatically detect the driver type (DALI/ 0-10V) and provide the dimming interface accordingly. There is 2 wire interface between control mechanism and driver.
0-10V is analog type dimming and DALI is digital interface. How it can be done Any idea.


texts: Low temperature batteries for use in Arctic

texts:
I've been checking the forum and Google but still haven't got precise solution to my current question. In short, we are looking for rechargable batteries for Arduino that survive under -40 Celcius degrees.

Our group is going to deploy several sensors in the Polar Region, Arctic, to study the permafrost.

These sensors are dispersed in the area around a community, within some kilometers. The data collected by the sensors are to be saved with Arduino-based nodes, and then uploaded to cloud for quasi real time.

Hence, the Arduino modules serve as dataloggers and LoRa nodes. In the community, we've got power line to power up the LoRa bridge. But all the end nodes out of community cannot access AC power source.

Lacking a source of power, the end nodes rely on batteries and solar panels.

There are several considerations here.

For example, sensing and LoRa transmission need to be set to very low frequency, like, once per 15 minutes, to reduce the power consumption. We would set it via programming, and set Arduino to sleeping mode for the rest of the time.

Here comes the question I'm having trouble with:

What kind of battery and solar panel should we use? The temperature on site is very low, going to -40 celsius degrees in deep winter.

Most commonly used battery types cannot survive these temperatures. We also need the battery to be rechargable, which could be charged with solar panel (of course, mostly during Spring to Fall while there is sunshine.)

Our technician used lead acid batteries in the past but the performance was marginal.

The batteries on some sites were severely damaged and even broken during winter.
And solar panel and power source regulator? We plan to shorten the operating time so we can reduce the size and cost of solar cells, but still, we need them to stay alive.

Any suggestions?


texts: Non-Invasive High Power DC current measurement

texts:
For one of my projects I need to measure if there is a DC current going trough the thick power cable. The current is DC, and my method of measurement has to be non-invasive.

The current going trough the cable will be anywhere from 1A to 50A. Also the measurements don't have to be precise (at all), I just need to know if there is current being drawn (flowing trough cable) or not.

I've found several solutions using current shunts, hall effect sensors but all of them have some upsides and downsides.

I was wondering if someone could suggest a cheap/simple solution for Non-Invasive high power DC current measurement?


texts: Distribution of charges in an electrostatic study

texts: I have a question concerning the capacitive coupling between two conductors. The capacitance C between the two is only a function of the diameter of the 2 studied conductors, the insulation thickness of the latter and distance between the two. My question is, since the charge on each conductor is equal to |Q| =|C*V| where V is the potential difference between the two conductors, the charge distribution should remain the same as long as V=1, right?


texts:
I am about to write a TCP/IP stack in Verilog. I would have thought this was a relatively common thing, and that implementations would readily be available online.

The obvious Google search for a TCP/IP implementation in Verilog does not point to many solutions. Are there ready and tested TPC/IP implementations written in Verilog for FPGAs?


texts:
So I think this this going to be a simple answer but I just cant really find anythign that confirms this for me.

This is the VCXO in question:
Q-Tech QTCV356

The control voltage range is 0.3V min, 3V max.

If this VCXO is controlled by a DAC that outputs 0 to 3V, some resolution is lost since the output of the VCXO will be unchanged through the 0 to 0.3V output range of the DAC.

Assuming this is true and that changing the components is not an option, I would think the simplest solution would be to bias the output of the DAC so that it outputs 0.3V-3V.

Am I thinking about this correctly?

And what is the point of having a control voltage of 0.3 to 3V rather than 0 to 3V?

Thanks for any help


texts: Can I use dc-to-dc converter to step up voltage of 20 3.7V 3Ah lithium-ion batteries connected in parallel?

texts: I want to use this 3.7V 40Ah powerbank to power my e bike's 48V hub motor. So would it be a bad idea to step up 3.7V all the way up to 48V? Would there be a huge Ah loss?


texts: What is the formula for measuring Antenna range?

texts:
According to example 1 of this website
The formula for measuring the antenna range is this => D = radical(2hR)
which R is 6400km for earth and h is the height of our antenna from ground.
So if we have a tower that has 100 meter height,the maximum coverage range for this tower is about 35.77km.
My question is , what is the coverage range of the specific antenna? for example yaggi , horn , dipole , parabolic reflector with ...
The formula above is just for the tower range, not for the antenna of specific frequency and gain.


texts: Minimum Current(not for switching) On a Relay?

texts:
I'm trying to understand how the pictured device works. It's a Sonoff WiFi controlled electrical relay. I was told that it is designed to control mains voltage only, and cannot be used to control a 5v dc current. This doesn't make any sense to me, because I'm under the impression that the relay which ultimately controls the current works by simply completing and breaking a circuit using an electromagnet to move the switch. If so, this would mean that the current may practically be as low as I want, as long as it's below the maximum voltage and amperage rating for the relay.

Am I correct in my belief that a device like this can be used to control a 5v dc current without modification, or do I need something specifically designed for lower voltages? If I need something different, then what do I need, and why?


texts: I want to connect 2 devices together using RS232.  I initially thought both devices used the power ground as the reference signal for their RS232 (they're powered by the same PSU) so I designed my RS232 cable just using Tx and Rx.  However, after some testing and some bad RS232 communication, I learned that one of the devices actually uses case ground (earth ground) as the reference signal.  If I connect the RS232 reference signal pin, the communication is flawless, but I want to avoid connecting my floating ground to earth ground (I believe this is good safety practice).  Is there someway I can create an isolated reference signal for the two devices to use?


texts: What are the demo 1 and demo 2 terminals on the oscilloscopes?

texts: I have seen almost all oscilloscope providing this demo1 or may be demo2 terminals on their oscilloscopes which has the square wave running all the time? I can't figure out the purpose of those demo terminals?


texts:
Can I simply hook up an opamp inputs, (either using a differential or in-amp topology that is/are also powered from a floating power supply),  across a device under test that itself has exceeding voltages for the opamp (<50Vdc)  ?

so idea is to build smth that uC's ADC can measure and eventually for PC to read (via serial).

The DUT can go as high as 50V and is only DC.
Differentially I am not expecting anything higher than 2-5V across the inputs, worst case.

Thus I was wondering, How does a multimeter achieve differential measurement ? Without worrying about the voltage that the measurand is actually at, as long as the voltage between probes remain in the spec, I'm fine...
(I do not want to build a multimeter (nor differential probes), but the functionality is the same...).

-> My understanding is that I should be able to hook up an independently powered opamp (dif-amp, in-amp ?) across another device's resistor, read out the voltage drop (by subtracting one input from another), without being connected to the ground with the Device Under Test. Right ?

simulate this circuit – Schematic created using CircuitLab

I have tried to simulate different topologies but to no avail. At least Micro-Cap won't simulate floating power sources that well.. it seems.. I get errors and strange values.

a) If simulation won't allow me to detect floating power source, do I really need to connect the DUT and my measurement circuit to common GND at one point ? - Meaning the common mode voltage range should become an issue as both systems are tied to single reference... for me it doesn't add up.

That's why I want to have a floating measurement circuit, so I shouldn't worry about grounding (such as a voltmeter), but that's where simulation fails for me and I am unsure.
Another idea was to take two opamps, make them as buffers (maybe add an amplification stage as well) and just read each of them with separate ADC inputs and do the subtraction in Software - anyway my problem persists - Can an opamp measure these differences when being powered from floating power ?

I'm also referencing few topics, which should've lead me in a somewhat correct direction, but seems I'm missing something. I also started to think about possible grounding issues and reference points:

Differential Voltage Measurement

A question about differential measurement system


texts: How to isolate (audio) components supplied with the same battery?

texts:
We built a very simple circuit out of prebuilt components: a battery, a signal generator, an amplifier, and a speaker. The signal generator (i.e. a Bluetooth player) and the amplifier are supplied with the same 12v battery.

The problem is that although the circuit works (mostly) as expected, one of the components (I guess it's the amplifier) generates a high frequency noise coming out of the speaker.

We just identified the following facts:

Adding a resistor to cable (B) won't decrease the noise (even if the music is completely silenced)
Supplying the signal generator from a separate battery makes the noise disappear
Disconnecting cable (A) won't break the circuit, but increase the noise

Not sure whether this is enough informaion, but I wonder whether there is a way to make the noise disappear without adding an additional battery.


texts: Are two (or N) resistors in series more precise than one big resistor?

texts:
Let's say I have one 2 kΩ resistor with 5% tolerance. If I replace it with two 1 kΩ resistors with 5% tolerance, will resulting tolerance go up, down, or remain unchanged?

I'm bad with probabilities, and I'm not sure what exactly tolerance says about resistance and its distribution.

I am aware that in the 'worst case' it will be the same; I'm more interested in what will happen on average. Will the chance of getting a more precise value increase if I use a series of resistors (because deviations will cancel each other out)?

On 'intuitive level' I think that it will, but I have no idea how to do the math with probabilities and find out if I'm actually right.


texts: What is the best/safest way to wire a 200V fan in the USA, using 120v or 240v?

texts:
I bought a surplus fan/HEPA filter unit for using in a clean room. The wiring diagram is here.

I want to connect it to a power cord and plug it into the wall.  I know basic electric, but I'm not sure about the issue of using 240v to run a 200v motor.  Any advice would be much appreciated.


texts: PCB Reflow in oven, will solder melt before VRM's, caps etc get damaged?

texts:
From Wikipedia:

  Alloys commonly used for electrical soldering are 60/40 Sn-Pb, which melts at 188 °C (370 °F), and 63/37 Sn-Pb used principally in electrical/electronic work. 63/37 is a eutectic alloy of these metals, which: has the lowest melting point (183 °C or 361 °F)

Having previously successful done a 'reflow' of a computer Graphics Card in a home oven in my only attempt of this kind, I am now considering doing the same for a motherboard which, while still functioning (occasionally, it will fail to start up or black screen mid use, and yes, it is the motherboard).

However with my motherboard containing a wider array of PCB components like ROMs etc and a fair bit of 'plastic' composites like ram slots (they have hundreds of traces so not practical to solder them all of in order to remove) I am more skeptical this time around.

My assumption is being PCB components that these surely adhere to some sort of temperature resistance requirements? However at 170-180 °C that I would be baking at I'm really unsure if things like capacitors, vrm's Vcontrollers and the 'plastic' bits like ram and PCI slots could handle the heat.

I'm hoping the community here can help me out on this one, as searching online mostly churns out baking laptop motherboards which lack these 'plastic' bits.

The board in question looks like this:


texts: Put one value in PORTA, and another value appears (PIC24 from Microchip)

texts:
I am doing a small code for PIC24FJ1024GB610 from Microchip, where I want to test PORTA

The code Below

#include <xc.h>

#pragma config FWDTEN = OFF
#pragma config FNOSC = FRC
#pragma config ICS = PGD2

unsigned int Pattern;

void Ports (void)
{
    TRISA = 0x0000;//all outputs
    ANSAbits.ANSA6 = 0;
    ANSAbits.ANSA7 = 0;
    ANSAbits.ANSA9 = 0;
    ANSAbits.ANSA10 = 0;//all digital ports

    LATA = Pattern;

}

int main (void)
{
    Pattern = 0xBBAA;

    Ports ();

    while(1);

    return 0;
}

What I expected to happen was:

Pattern is declared as an unsigned int
at main () Pattern = 0xBBAA
Program calls Ports ()
PORTA configured as Output TRISA = 0x0000
PORTA is configured as Digital ANSA = 0x0000
LATA = Pattern, if I debug the program, I would expect LATA = 0xBBAA in the SFR window.

When I debug the program, and open the SFR window, I get LATA = 0x82AA, as you can see in the screenshot below.

Helpful info:

I am using Development Board "16/32 Explorer Development Board", from Microchip
IDE: "MPLAB X IDE"
PIC24FJ1024GB610 Datasheet

Any help is appreciated.


texts: AMS1117 33 sot223: is it ok with ceramic capacitors?

texts:
This is the datasheet of voltage regulator that I would use:

http://www.advanced-monolithic.com/pdf/ds1117.pdf

Is it possible to exchange that 22uF with an equivalent (or larger) ceramic instead of electrolytics? Cause I would use 1206 SMD components.

Also, in some websites I did find schemas with 2 capacitors on INPUT and 2 on OUPUT, on parallel, both of 22uF + 100uF.

In effect, I did print same pcb layout (feeded power from a Samsung Charger via MICROUSB and converted down to 3V3) with electrolytics capacitors and it works very well (tested with a multimeter, 5V on INPUT and 3V3 on output). Is it an exageration?

Thank you for both the answer

Edit: another schematic with this AMS1117 is the module provided on Aliexpress.

This is the image (mirrored...), you can read 104+106 on input and same on output.

I did test them from a friend and seems to work... What do you think about them?

On another image, seems clear that 104+106 on input and 104+106 on output. Is possible that supplier does not respect the datasheet?