texts: Question on replace of Inductor Coil in a FM Transmitter

texts:
I am making a 2 Watt FM transmitter. The transmitter's inductor is somewhat like this :-

The resistor is part of the transmitter circuit. I am little confused with the inductor and not sure how to make it. I have small ferrite toroid. Will it work?

And 0.8mm CuAg wire means 20AWG. If I replace it with #23 or #26 wire, how many turns would be applicable? For L2, would a normal insulated copper wire work? And should it overlap L1 on the ferrite, or co-exist on the ferite beside L1?

I am referring the below circuit:

Any idea, if L1 and L2 can be replaced with a single air-core Copper Coil?


texts: Is it safe and efficient to charge a Li-Ion cell from mixed alkaline cells?

texts:
I’m a live sound engineer by day and very novice electronics hobbyist. Hoping for some advice on a small project I'm attempting.

Although the use of rechargeable cells in my world are becoming more common, alkaline cells are still in heavy use for wireless audio transmitters and receivers. Unwilling to take the risk of a $1 cell running flat during a show, alkaline cells are changed each show. These half-used cells still have usable capacity, yet are thrown out or recycled. It's very common while working large cast theater shows <48 AA used cells are trashed or recycled each night.

In an effort to claim this unused energy from half spent alkaline batteries, I’ve been using a very simple rig using 4 “used” AA batteries which power a Li-ion USB charger which charges a single 18650 cell. I closely monitor the current draw, alkaline cell voltage and temperature. This 18650 cell is used in a larger battery pack to power other uses.

If trying to eliminate the risks of mixing cells of unknown capacity and age, could I use a singe AA cell with a DC to DC step-up (.9-1.5v to 5v) into a Li-ion charging type circuit (i.e. TP4056)?
If this is a viable path, is it dangerous or harmful for the 18650 to charge at a very low rate (>100mA) and/or long charging period?

Thanks for any insight and help.


texts: What is the typical value of a scope's blocking capacitor used in AC coupling?

texts:
I find many information about what AC coupling is about as following:

But not a single of them mentions the typical value of the blocking capacitor used in a scope's AC coupling. No quantitative information.

Considering a scope in 1x setting, input resistance of a scope is typically 1Meg. But what is the typical value of the scope's blocking cap. used in AC coupling? And why?


texts: Have SO(P)X components 2.54mm, 1.27mm or smaller pin spacings?

texts:
I'm a bit confused about the pin spacings of SO8/SOP8.

Example: in Detail 2.54 SOP8, pin spacing is 2.54mm.

However, according to Small_Outline_Integrated_Circuit, fragment:

  Small-outline package (SOP) After SOIC came a family of smaller form
  factors, small-outline package (SOP), with pin spacings less than 1.27
  mm:

This seems to contradict each other.

So is SOP8 2.54mm, 1.27mm or less than 1.27mm? Or can it be anything?
And SOIC8 always has a larger pin scaling than SOP8 (1.27mm, versus < 1.27mm)?

Or is there a standard and a lot of (especially Chinese) manufacturs do not follow them? And what about the Toshiba example?


texts: Two nRF24L01+/Arduino UNOs don't connect

texts:
I am trying to establish simple ping/pong communication between two nodes connected on two arduino UNOs using this guide http://maniacbug.wordpress.com/2011/11/02/getting-started-rf24/ and the RF24 library. So far it seems that the wires are connected well because I am getting addresses for both nodes :

RF24/examples/GettingStarted/

ROLE: Pong back

*** PRESS 'T' to begin transmitting to the other node

STATUS       = 0x0e RX_DR=0 TX_DS=0 MAX_RT=0 RX_P_NO=7 TX_FULL=0
RX_ADDR_P0-1     = 0xf0f0e1d23c 0xf0f0f0f0d2
RX_ADDR_P2-5     = 0x69 0x96 0xa5 0xc3
TX_ADDR      = 0xf0f0f0d269
RX_PW_P0-6   = 0x20 0x20 0x20 0x20 0x20 0x20
EN_AA        = 0x00
EN_RXADDR    = 0x3f
RF_CH        = 0x4c
RF_SETUP     = 0x07
CONFIG       = 0x0f
DYNPD/FEATURE    = 0x00 0x00
Data Rate    = 1MBPS
Model        = nRF24L01+
CRC Length   = 16 bits
PA Power     = PA_HIGH

What disappoints me is that by using GettingStarted example http://maniacbug.github.io/RF24/GettingStarted_8pde-example.html both nodes are working but they are unable to establish connection.

My first question is: as every network equipment has a MAC address to be identified, shouldn't all rf24s have something similar ?

I have seen this :

// Radio pipe addresses for the 2 nodes to communicate.
const uint64_t pipes[2] = { 0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };

is this some kind of MAC address or id ?

I am so thrilled about those sensors and I can't wait to make them talk :)


texts:
could you please review my layout?
It's the top side where the antenna is actually placed.

It's bottom side, here I've placed a matching network, LNA (U5)2 and SAW (FL1). The length of the trace between the antenna's output and  IC input is about 15mm (without capacitors and LNA/Filter's size).
I used kicad's calculator to get trace width - 1mm (coplanar trace, dielectric height - 1.6). Both sides of the board are covered with a ground polygon.

It's a recommended layout from the antenna's datasheet. But I've used the matching network from the  LNA's datasheet.
[]
Here is schematic


texts: I am looking into creating an illuminated string of leds where the individual LEDs are not visible, but that a shape is illuminated. The shape would be a various sized rings the biggest being about 1ft in circumference. Here are some example pictures of what I am thinking of. Now, a caveat is that it has to be the same on both sides. That being that the top and the bottom both have to be illuminated. I am just asking what sorts of LEDs and materials that I should be looking into to achieve such a result.


texts:
I would like to add a low noise amplifier and a power amplifier to the ESP32. As you may know there is only one RF output on the chip.

I was thinking of adding an RF switch, and switching between receiving (ANT to LNA to ESP32) and transmitting (ESP32 to PA to ANT).

Where you I place my switch on the schematic ? At the end (A) or at the beginning (B) ?

Also should I worry about PA output EMI being picked up by the LNA ?


texts:
I was wondering about this part of a circuit diagram. I believe the component marked as JP12 is a DC barrel connector, which I thought had three pins. One to detect input, one with V+ and one with ground.

However I thought this device was also receiving 5.0V from USB. The diagram shows pin 1 of the DC connector directly connected to the VBUS line, does this mean the DC connection is also powering the USB device. If so, what is pin 2 being used for.

Also, I have no idea which of the three pins in JP12 is supposed to be ground. Am I mistaken, and this DC connector does not supply ground?


texts: Is it possible to use a digital potentiometer as a digital rheostat?

texts:
With a three-terminal analog pot, you can use the middle and one of the outer terminals for it to function as a rheostat.

As it happens, I need a digital rheostat in my circuit but I only have digipots on hand: an MCP4151 and an MAX5481. Since this is a one-off project and I'd rather not wait for a digital rheostat to be delivered, I'm wondering if it's possible to use a digipot as a digital rheostat, perhaps with some extra circuitry if needed?


texts: Question on Logic circuit and Karnaugh Map

texts:
I got this question from a university site and thought of attempting it to test my knowledge in Logic circuits, Boolean alg and Karnaugh graph. Problem is, I have been scratching my what logic circuit is coming out; I am not able to translate this into a known Boolean Algebra.

The Question:

A vehicle seat belt circuit is such that the car should only start if the driver’s seat belt is
fastened and either the front passenger seat is unoccupied or the front passenger seat is
occupied and the passenger seat belt is fastened.
Obtain a truth table, boolean equation and Karnaugh graph.

I need help on the truth table.

Suppose:

A: Driver seat belt

B:Passenger seat occupied

C:Passenger Seat Belt

Considering A, B and C, I get this truth table, but see my comments below:

   A    B     C   B??C    A AND(B??C)
  ---  ---  ---   ----    --------
    0    0    0   1       0
    0    0    1   1       0
    0    1    0   0       0
    0    1    1   1       0
    1    0    0   1       1
    1    0    1   1       1
    1    1    0   0       0
    1    1    1   1       1

When I consider B and C (Passenger seat occupancy and Passenger seat belt:
When there is no passenger, Passenger seat belt does not matter as long as driver seat belt on. these are represented by B??C. The problem is, I am not able to figure out what Boolean condition this is: AND, XOR, NOT, etc. This is what is making it difficult for me to produce the resulting Boolean Algebra for subsequent questions. Help.


texts: Coaxial cable, resistor and oscilloscope

texts:
I'm studying the trasmission of signals though coaxial cable; I'm using a coaxial cable (of course!), an oscilloscope, a generator an some different endings. This is the scheme:

I was told that if I use a very long cable that has impedence \$Z_0= 50 \Omega\$ and put, at the end of it, a resistor of \$47\Omega \$, the signal will be reflected.

I have obtained this:

If I have correctly understood, the height of the step pointed by the green arrow is the half of the V given by the generator.

I can't understand why the step pointed by the red arrow is shorter than the one that is on the other side. And I can't understand what's the physical meaning of the step pointed by the red arrow.

Then, I have terminated the cable with a short circuit and I have obtained this:

Could you explain me what's up at the points indicated by the two arrows and the yellow and red points?

Then, I have terminated the cable with a resistor of 100 ohm and I have obtained this:

Could you explain me, why the step pointed by the green arrow is higher than the step pointed by the red arrow?

This is the last image:


texts: Strategy for powering surveillance cameras

texts:
I would like to install 16 surveillance cameras
All the cameras are connected to a DVR, 25 meters away (at most)
All cameras are powered by 5V-DC, around 3W-6WS for each camera.

I have two strategies for the powering the cameras.

  Use standard 220V-AC already spread around and have a small AC-DC converter for each camera.
  Install a Main AC-DC (around 150W) near the DVR and connect all the camera with 12AWG wires.

There are many pros and cons for each strategy. I would like to get your opinion on the subject. Feel free to assume that 16 small power ACDC costs like one high power ACDC.


texts: I saw in some screenshots that people had VHDL modules inside another VHDL module at Sources Window in ISE Project Navigator. Every time I try to add new VHDL module (using RMB -> New Source...) it is created at the same hierarchy level as all others VHDL modules. Suppose that I make some complex component that consists of some simple components. Should I attach VHDL modules describing simpler components under the VHDL module describing complex component or should all modules be at the same level of hierarchy? I wonder because xxx.ucf file is always under the Top Module.


texts:
Hello I am planning to use an Arduino to make a joulemeter for a current range of 0-30 amps and voltage range of 0-24V. The voltage measurement is fine but I have questions about current measurement.
For measuring current, I plan on using a MAX4081TAUA+ to amplify voltage across a shunt.

The Arduino internal ADC can read up to 5V and the voltage gain of the amplifier is listed as 20V/V. From my understanding, at maximum current, the voltage across the shunt resistor should be 5 / 20 = 0.25, so the resistance of the shunt should be about 1m. Is this correct and will this give a reasonable accuracy?
Thank you.


texts:
It is just a general question. I have designed some micro controller boards with On-Board EEPROM. This EEPROM is to store some configuration parameters for program like calibration data and system IDs. Now when i want to write some configuration parameters,I load some program to write to that specific EEPROM address and run once. Then I load application program.
I think this not the most efficient way to do that task. What is general method to write EEPROM data.
One way to provide some external interface to EEPROM and then using some PC program write direcly into it. But I guess this exposes external interface andleads to vulnerable system.
Other could be to add methods in application program itself using serial port and define some API to change those parameters.
I just want to know the acceptable practice in community from accessibility and security point of view. If it involves any hardware change i can incorporate in future design.
Thanks

EDIT-
On-Board EEPROM is external EEPROM.


texts: Current limiter - charging battery from battery

texts:
I'm planning to charge auxiliary battery from car's alternator, by using voltage sensitive relay to connect positive poles of car's battery.

The only obstacle now is that auxiliary battery (12V) allows maximum charging current of 20A. Therefore I need current limiter in series with relay.

Which is the most simple circuit that I can use?

I've read that people use light bulbs due to their non-linear behaviour. In that case how can I calculate the needed wattage of (12V) lightbulb, to limit current to 20A?

EDIT: In other words I need 12V lead-acid battery charger that gets power from another 12V lead-acid battery with charging limit of 20A

EDIT:
System info:

Car battery: 100Ah 760A start current - regular lead-acid car battery
Auxiliary battery: 100Ah (C20), max charging current: 20A, 500A/ 5s start current - cyclical solar battery
Wires: 2x 10mm^2, cca. 2x 3m, copper


texts: Alternatives to RJ45 ethernet connections?

texts:
I have a system where two boards need to communicate through a serial bus with several lines --- rates are in the order of up to 3MHz.  The boards will be several meters away (say, 3 to 5 meters / 10 to 15 feet away).  I'm planning to use a differential pair for each signal that needs to be transmitted.  In particular, I'm planning to use LVDS, using TI's SN65LVDS1 driver and SN65LVDT2 receiver.

My current plan is to use ethernet cables, as they should comfortably and reliably carry those signals.  However, two inconveniences are: (1) the connectors are bulky (compared to the size of my board's components); and (2) I don't want anyone to go and connect these boards to an ethernet switch, or in any case expect that they are intended to be connected to a LAN or the Internet.

Another inconvenience --- or rather, peeve --- is that I actually need to transmit five signals + GND. That exceeds the 8 pins of the ethernet cable, so that aggravates issue (1) above --- the connectos are already bulky, and it turns out I need two of them;  or one RJ45 and another of some different type, which is also a peeve.

Are there any alternatives that you could suggest?  I could perhaps attempt to use flat ribbon cable with header connectors --- I could leave GND wires in between differential pairs to avoid cross-talk;  but I fear that the capacitance between the two wires of each differential pair may be too high, and transmission up to 3MHz may be challenging. Any thoughts?


texts: Crystal oscillator producing straight line only

texts:
I have replicated a crystal oscillator circuit from internet, but the output waveform is a pure DC rather than the expected sine wave. Below are my circuit diagram and the simulation output from Multisim.

Kindly help me figure out if there is something wrong with this circuit and what can be done to resolve this.


texts: Is it common for internal pull-up resistors to fail? or what would cause them to become intermittent?

texts:
I have a board based on an ASIC ARM Cortex-M3 that after months of work suddenly started to report spurious button presses.  The ASIC is not our design, but a reputable company's.

The buttons schematic is given below.  The pin is configured as input with pull-up resistor enabled.  The resistor's value is about 30KOhm.

When measuring the pin-side with a DMM, I see the value floats around.  Sometimes it is 3.2V (=VCC, chip range: 2.1V to 3.6V) and other times jumps around floating between 0.6V to 1.0V.

There are no issues of humidity/condensation (9% RH), no dust or other objects on traces.
And this is the ONLY board that suffers this. Other manufactured clones of this board work without any issues (so far anyway).

The only thing I can think of is that something is making the internal pull-up flicker.  Is it common for the internal pull-ups to give way?  What else could be causing this?

R9,R12 are 2.2Kohm, and C10,C11 are 33nF.


texts:
I currently have a 2000 VA UPS inverter that is powered by a 24 volt battery. I want to increase my load capacity and was suggested to buy a 4000 VA system that runs on 48 volts. However, as I don't want to let my current UPS go useless, I was wondering if I simply bought another 2000 VA UPS inverter of the exact same model and an extra 24 volt battery to power it, will both of the UPS be able to support up to 4000 VA if their outputs (220 volts AC) were connected in parallel?

Let's say if the above works, are there any down sides to this compared to the single 4000 VA unit? Will the above be able to power a small 12000 BTU air conditioner or 11 cubic feet refrigerator and will it need any circuit breaker if one unit suddenly failed and output dropped to 2000 VA?


texts: Host and device protection needed for designing for USB type 3.0 powered electronics?

texts:
I am designing a switch-mode variable power supply (that can boost) intended to run on USB type 3.0 (be powered by a PC/laptop USB port say). Being that I am quite naive to computer electronics I am instinctively unsure what happens if I short my power supply accidentally, although I assume it varies between machine.
My question is then what protections should I implement on my end to reasonably expect it to work on most machines without breaking something (i.e. strict current limiting and whatnot). Thanks


texts: Can I realize displaying action potential of a plant in a very minimal setup?

texts:
I would like to show an experiment for kids on the Science day this April in our institute. It is inspired from this Backyard Brain's experiment. This experiment shows the action potential captured from the plant when the leaves shrink and displays the waves on a CRO. In my locality shy plant is available. But I don't have enough money to buy Spiker box kit from Backyard Brains. So I thought about another idea to realize the same.

Can I use TI's INA111 chip to amplify action potential from shy plant? I am intending to do this on a breadboard. Basically I am thinking to connect a wire from the plant stem (and of-course properly grounded) and connect it to the input pin of the chip and then visualize the amplified signal.

EDIT 1: Specification of IC chip INA111 below from its datasheet :

EDIT 2: The Backyard Brain's spikerbox experiment in short is as follows. The spikerbox is a bioamplifier (instrumentation amplifier), which picks very tiny signals. So they connected the input wire of the spikerbox kit to the stem of plant and ground the other wire in earth properly. Also conductive gel is applied on the stem wire interface. Then the plant leaves are disturbed, which makes the leaves to shrink, which causes the action potential to pass through wire to spikerbox. From the output pin they connect the signal to CRO and you can observe the wave for the response of shrinking leaves.

MY QUESTION   :  So my specific question is as follows. I have resources like breadboard, DC power supply, few basic components like resistors, IC chips like AD623 or INA111, laptop with linux and free oscilloscope software etc. Can I realize displaying action potential in a very minimal setup ?


texts: How to remove the negative component of a sine wave?

texts:
The following is the schematics of a simple circuit I'm working on, It filters and amplifies an electret condenser microphone's signal to get an output ranging from 0 to 9V (to drive an equalizer like leds not a speaker):

simulate this circuit – Schematic created using CircuitLab

The mic signal passes first through a low pass filter with a cutoff frequency of around 20Khz, then gets coupled with a 47nF capacitor, then gets offset by 1/2 VCC by a voltage divider, then amplified 1000 times using 3 noninverting amplifiers with a gain of 10 each.

Now the next stage I want to clamp the negative part of the signal, to do that I put a reverse biased diode after a coupling capacitor. But after testing the signal appears to pass through unchanged. Why is it not getting clamped?

Update:

If I disconnect the non-inverting input of the last opamp from the diode and measure the voltage at the junction between C6 and D1 I get a nice clampped singal between -0.6V and 3V (I had to increase C6 to 100uF though).


texts: Why there are live and neutral wires attached to house's wall sockets

texts:
If AC voltage is alternative,  why there are two (Suppose there is no earth wire)  wires attached to the wall socket:  live or hot, neutral wires? And I think that in small home generators there is no need to specify which wire is the live wire?

I've read that the neutral wire is connected to the ground. Where it's connected, I mean at the house or somewhere else ?


texts: How do I detect that a tilt sensor has been tilted "shorted" when polling only every minute?

texts:
I thought about modifying this circuit (Momentary switch power: press to turn on, microcontroller can turn itself off), but I wonder if something simpler might work (or if someone had a better idea)?

I'm using the Atmel SAM R21 Xplained to prototype a device.  I want to detect if a tilt sensor has been activated, but I don't want to continuously poll its stated so I can save power.  I'd like to poll, let's say once a minute, send it's state over 802.15.4 to the cloud.

Here is the idea I've come up with:

By using a digital output to charge a capacitor and the analog input to detected it's voltage, track the capacitor's voltage to see if it got shorted out within the 1 minute interval.  The circuit would look something like this:

simulate this circuit – Schematic created using CircuitLab

The algorithm would be:

Initially charge the capacitor.
Loop forever -
Detect, if the voltage dropped significantly, send a message.
Charge the capacitor.

Thanks,

Greg


texts: Switching between 2 power supplies upon dropping below cutoff voltage efficiently

texts: I am making a circuit which is powered by a lipo battery of 11.1V(3.7V*3). I need to check for the lipo's under-voltage so that the circuit automatically switches to a second lipo when the first one drops below the cutoff voltage. I am open to using arduino and relays but no diodes(as they lead to large power loss).


texts: Can non-rechargeable batteries be used in place of rechargeable ones?

texts:
I am aware that attempting to charge a non-rechargeable battery is a terrible idea, and I have no intention of doing so. But supposing that, in a pinch, I needed to use non-rechargeable batteries in a device that originally came with rechargeable ones, and I don't use the charging cable the device came with while the non-rechargeable batteries are in use, could there still be a problem? How long would it take to manifest? Would it damage the device or batteries?

Sorry if this is off-topic, I'm thinking my question is along similar lines to this one.


texts: Why are relays so frequently driven by optocouplers?

texts:
Since the advent of the many microcontroller development boards, like Arduino, there have been a number of relay modules sold to drive mains AC loads.

A lot of these seem to use an optocoupler, driver transistor and a relay to drive the load (example on Amazon)

Why are they implemented like this?

Some of my thoughts:

Relays provide as good or better isolation than most optocouplers
There is still a driver transistor present, so it is not component
saving
There is still inductive kickback protection, so it is not
component saving
Optocouplers are not as cheap as transistors, so additional cost compared to just a driver transistor
There is no need to meet any regulatory requirements as these are DIY products
I have never seen small mains relays driven by optocouplers in commercial equipment
A number of these boards don't seem to be designed brilliantly (no regard to clearance or creepage), so even if the optocoupler is simply to provide two layers of isolation, the board fails at this.


texts:
In this circuit when D=0 and Clk=0  the value passes from w-x-y-z and z= 1. So at z= not D
So this path constitutes what is called setup time of the flip flop. But at the same time the value at D can also move to the slave flip flop is'nt it  ? As when clk=0 the 3rd transmission gates pmos will be on and it will be able to pass the zero at x . So how is the master slave action taking place. Is it that the 3rd transmission gates pmos cannot pass a strong 0 so it gets ignored ? If that is the case if i remove the inverter at input ill get a 1 , and so it will pass that strong 1. Please someone explain me this operation without ignoring the second slave latch when master is receiving input


texts:
I was looking at the SN74HC164N shift register datasheet and I noticed something that intrigued me:

There are 2 input signals A and B, but they are NAND'd together to produce the final output. My question is why? I suspect it's so the shift register can have 2 different input sources, though I'm not sure why they would embed that on-chip.

If that's the case and I only have 1 input source, can I just tie the two together and have a 3-wire configuration with DATA_IN, CLR, and CLK?


texts: What is the "socket" on Hirose DF13-series jumpers?

texts:
For this pre-crimped wire family with a "socket" at one or both ends:

Hirose H*B**-101**-**

with these mechanical drawings:

All units expressed in mm. Here is an example device. What is the socket standard? Is this quick connect? If so, what is the accepted tab size?


texts: Does there exist any drop-in USB I/O controller?

texts:
I need to control 17 digital outputs and 1 digital input from software running on a generic PC. The two interfaces that I can expect to always have available are USB and Ethernet. I don't necessarily need low-latency access to the IO ports, and I only have to read the inputs once every few seconds, but I do need to toggle the outputs at precise time intervals.

To achieve this, I thought the best approach would be to get some generic, low-cost MCU with 18 IO pins and USB support, and program it to accept a buffer of simple time-stamped commands over USB, which it would queue and then execute at the proper times. Instructions would translate to English like: At +1.2s: output 1100101 00000100 0000 or At +1.3s: read inputs.

Then I realized that what I was about to create is totally generic - it can be used in any application, not just mine. This got me thinking that something like this may already exist as a commercially-available product (a USB plug and MCU soldered to a board with pin-holes for the I/Os). But I can't find it, and I'm not sure what keywords to search for. Does anyone know if I can buy something like this?

Edit: After asking this question, I came across this related post: USB to GPIO module


texts: Why are two maximum power dissipation mentioned for this transistor?

texts:
I am wondering why manufacturers mention two different maximum power dissipation values for transistors like 2N1613:

Does it have anything to do with whether a heatsink is used or not?


texts: How can I recognise cable connector? For example I have here 2 connectors, but basically is there any web catalog with list of the most known connectors?


texts: Illegal sequential statement right shift multiplier

texts:
I am trying to implement a Right shift multiplier and that is supposed to be the data path. Why does this code generate this error ?:

  Illegal sequential statement.

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_signed.all;

entity data_path_module is
port (
a_in        : In    std_logic_vector(3 downto 0);
b_in        : In    std_logic_vector(3 downto 0);
rst_n       : In    std_logic;
p_in        : In    std_logic_vector(3 downto 0);

a_out       : Out   std_logic_vector(3 downto 0);
b_out       : Out   std_logic_vector(3 downto 0);
valid_out   : Out   std_logic;
p_out       : Out   std_logic_vector(3 downto 0)
);
end entity data_path_module;

architecture data_path_module_df of data_path_module is
signal tmp : std_logic_vector(3 downto 0);
begin
P1 : process (a_in, b_in, rst_n, p_in)
begin
p_out   <= p_in + b_in when (a_in(0) = '1') else p_in;
a_out   <= b_in(0)  & a_in(2 downto 0);
b_out   <= '0'      & b_in(2 downto 0);

valid_out   <= '1';
end process P1;
end architecture data_path_module_df;


texts: What is the fastest way to solve this circuit?

texts: Since V+ and V- are both @ 0 volts I thought I could combine these resistors in series and parallel, but that gave me the wrong answer. (The right answer is Vout = -4IR)


texts:
Suppose I have a half-duplex LVDS source that I want to interface with a full-duplex LVDS device operating in a half-duplex capacity (i.e. the full-duplex device has both a TX and an RX interface, but they don't operate simultaneously)

The half-duplex source goes hi-Z when it is receiving.
It drives its outputs when it's transmitting.

Just tying the TX and RX pairs together seems like a bad idea--the output driver on the half-duplex device would fight the output driver on the full-duplex device (unless the full-duplex device output driver goes high-impedance when there's no data).

Should I use some combination of a MUX and a selector? My switching logic would have to determine whether the output of the half-duplex device is high-impedance or not.

Here's an example schematic:


texts: Can anyone please help me with this ETAP Project?

texts:
I'm trying to run the load flow study, but instead I'm getting this error.

Error 101-01: [Bus 2] Bus base kV is out of 40% range from bus nominal kV.
Error 722: [XFMR 1] 2W transformer secondary kV is out of 40% range from bus nominal kV.

Here's the screenshot of my project:

I honestly don't know what's wrong, I'm literally doing everything as instructed, but still getting the errors.

Here're the instructions:

Bus 1 is fed by the power grid (ID: Utility) with the rating of Rated kV: 4.16, 3-Phase SR Rating: 500 kVAsc, and 3-Phase X/R: 12.

A heater (ID: HTR 1) with the rating of 50kW and 85% PF (use the calculator of theloading page) is connected to Bus 1. (Hint: heater is a static load).

HTR 1 is protected by the fuse (ID: HTR1_FU): ABB (Manufacturer) & Max kV:4.16 (Use the Library to filter), & Cont. Amp: 8.

Bus 2 is connected to Bus 1 through a cable (ID: CBL 1), a breaker (ID: Bus 2_BKR), and a step-down transformer (XFMR 1).

CBL 1, which is directly connected to Bus 1, is: Freq: 60, Type: CU, kV: 5, #/C: 3, Insul: EPR, Source: KERITE, and Install: Non-Mag (Use the Library), Size: 1/0, Length: 50 ft.

The rating of XFMR 1 connected to the cable is Prim: 4.16 kV, Sec. 0.48 kV, Power Rating: 300 kVA. Use the Typical Z & X/R option at the Impedance page.

Bus 2_BKR, which is feeding Bus 2, is Cutler-Hammer, HMCA, 0.48kV, 800 A (Use the Library at the Rating page). The rating plug of its trip device is 500 Amp.

LT Pickup: 500 Amp & Short-time Pickup: 3500 Amp & St Band: Max (Use the Trip Device page. Deactivate the Ground protection). Keep in mind that each breaker has a Trip Device Unit which acts as the Brain of the breaker.

Update the ID of the bus to Bus 2 if you have not yet done that.

The node between CBL 1 and XFMR 1 has the ID of Node 1.

Bus 2 is feeding a lumped load (ID: LL 1) with the rating of 200 Amp and 85% PF.

Update the Load Type so that it is 50% constant kVA and 50% constant Z.

LL 1 is protected by a breaker (ID: LL 1_BKR): Cutler-Hammer, HMCA, 0.48kV, 800 A (Use the Library at the Rating page). The rating plug of its trip device is 500 Amp. LT Pickup: 500 Amp & Short-time Pickup: 5000 Amp & St Band: Max (Use the Trip Device page. Deactivate the Ground protection).


texts:
Please excuse my ignorance.  I need your advise and clarification on something.  I'm using the 18f4550 and I'm a little curious about the communication protocols.  I am not using the USB features.  It has 1-EUSART, and 1 (SPI/I2C) comm.  My question is, the EUSART and SPI seem to share pin26 (on the 40pdip).  I need to use both.  Is it normal for 2 comm protocols to share a pin and just toggle the config of that pin throughout the program?

Are the SPI devices on that line going to be confused at the UART data they see on it, and vice versa?  How likely is it they could react to some signal from the other protocol?  Or is it good practice never to dual-use such a pin and spec a chip with 2 separate protocol pin allocations?

Thank you.


texts: How to estimate NMOS Cds+Cdb capacitance from VDMOS Pspice/LTSpice model?

texts:
I'm designing a fly-back converter and in order to calculate the switching frequency I want to know a method or formula of how estimate the Cds+Cdb capacitance of NMOS switch using the Pspice parameters given by the VDMOS pspice model.

Thanks in advance!


texts: Does connecting 4 LEDs in parallel use more current then connecting 2 in series if the resistance is high enough?

texts:
Is it possible to give LEDs varying current, without sacrificing efficiency? Basically I have 4 LEDs which could all use varying current, because they are different distances from the receivers. The top LED doesnt need to be as bright as the bottom LED, since it is much closer to the photodiode.

I expected that I would be able to get away with less power, since I could more finely tune the current going to each LED, but it seemed to require more power to work as well as the first circuit did. Is my thinking on this wrong?


texts:
I can't find any uF valued capacitor with a high Q-rating (~150) for my required frequency  (~100 MHz). I need a 3 uF capacitor of this kind to realize my filter.

I have found a good capacitor that satisfies my specifications, but it has a value of 100 nF.

In theory, placing 30 of these would do the trick. How about in real life?


texts: how to calculate the tpdhl / tpdlh for any given circuit

texts:
i am struggling on calculating the tpdhl / tplh i dont know how to calculate is there any algorethim for the way we calculate the time propagation high to low etc.. several questions asking to take the long path / short path but i really dont understand

for example  the full adder with 3 nand gates and 2 xor gate . seeing a soultion for this example will sure be really really helpful.

( you can choose random time for each gate just for the concept thank you again ! )


texts: Does Hz and bps mean same? Can a signal be transferred at rate of say Mbps on a channel bandwidth of few Khz?


texts:
I would like to program stm32f4 or possibly others from beaglebone (black) board.

Is it possible to load firmware over serial (uart) or somehow to the stm32?
Is it possible to use two stm32 , one for development other one for loading new firmware?


texts: Crystal oscillator load capacitance, again

texts:
There's a lot of seemingly conflicting information regarding how the load capacitance for a parallel resonant crystal is calculated. Faced with a lot of problems in recent years with non-oscillation and frequency inaccuracy, I'm asking the community's help to get to the bottom of the problem.

How exactly should the values of external load capacitors be calculated?

What's the reason if the oscillator completely fails to start with crystals from some vendor and only completely removing the external load capacitors help? Other vendors' crystals work fine and they advertise seemingly similar parameters (load capacitance, fundamental mode, parallel resonant).

Are all integrated XTAL oscillators in, say, microcontrollers, always Pierce oscillators? Does it have any relevance on the issue?

For reference, here's some information that I've found from the Web regarding the calculation of load capacitance. One IC vendor defines it like this:

One crystal manufacturer defines it like this:

Another website has this to show for an answer:

    The equation is C=2(CL)-(CP+CI)

C = crystal capacitor value
CL = load capacitance
CP = parasitic capacitance (wires, socket, traces)
CI = input capacitance (mcu itself)

Quite many seem to think that the load capacitance is the value the crystal manufacturer recommends for the external capacitors. This, to me, seems completely incorrect. (But, as it turns out, might still work perfectly ok).

One web page puts an emphasis on knowing the oscillator inverter's input and output capacitances and gives this answer:

Is there a one true answer to the question? It all seems very frustrating to me. Why doesn't an oscillator start? Why does removing the external load capacitors make it start? How should the external capacitors' value be calculated?

PS. Sorry I can't tell you exactly which ICs I'm working with. But I've seen this happen with quite a few during the years.


texts: Circuit Analysis with opposing batteries?

texts:
Hello Electrical Engineering stack exchange! I was taking a physics practice test and I ran into the following circuit

"What is the current across the 2 olhm resistor when the switch is open?"

Now I know that V=IR but I don't really have any idea on how to tackle this question because of the opposing batteries. I've figured that once the capacitor is filled that no current should flow there so the switch doesn't matter right?, but I'm just stuck. Since this is a practice problem I'm looking for an explanation on how to tackle these circuits with opposing batteries. Thanks!


texts: Can i send a reset signal through the serial port?

texts:
I want to send a signal through the serial port to restart a modem, enfora gsm1218
(see datasheet http://www.testech-elect.com/enfora/pdf/GSM1218HR.pdf) is it possible?

I know that an AT command like AT$RESET exists to reset the software configuration, but I would like to hardware reset the modem itself as opposed to a software reset.


texts: How to re-initialize CANbus in case of an error at stm32f4 series

texts: I have to set a scan program to re-init canbus in case of errors such as disconnection of Rx-Tx lines, or other errors types. When any error is solved, my program will detect and re-init. But are there any approaches to solve this problem ? I am open to any logical idea.


texts: Simple circuit to give a pulse to a IC pin once?

texts:
I have an IC that is activated when pulsing a pin high, the pin should be keep floating after the pulse. The circuit is powered using a battery, and that IC then wake up everything else (Regulator, MCU, etc).

I'm looking for something like this:

Battery -> Pulse to the pin -> IC wakes up -> IC wakes up everything else

I'm trying to guess how to do that in simple terms, I mean without adding even more complexity to the circuit.

I have tried bridging the pin to the + of the battery manually for a moment (< 1 sec) and it works, but only after removing the + from the pin.

So the question is: How do I create a brief pulse using simple components? It is possible?


texts: Mechanical Keyboard PCB: Single Row Failure

texts:
I’ve got a weird issue on my hands and could use some advice. I built a mechanical keyboard and it worked for about a week, before the number row stopped working (no liquid damage or vibration/physical damage). I have a multimeter, but little experience in using it, so I probably haven’t been as through as I could. Anyway, here is what I’ve tried:

I’ve checked that the entire top row is connected to each other.
I have shorted ground to hot on a single key and it typed the entire column on the keyboard.
I’ve found a pin on the microcontroller that is connected to the top row, but not the other rows, and it seems to be correctly soldered to the board.
I’ve re-flashed the firmware to default.
I’ve tried different computers, and cables.

I had previously been cautious of the integrity of the micro-USB connector, but don’t know how to verify that its ok with the multimeter. Even if the board is just ‘dead’, I’d still appreciate knowing what some of the potential issues were. Does anyone have any ideas?

Here is a photo of the board:

And a close up of the microcontroller:

And a close up of the top right of the board:


texts:
I am looking at an accelerometer(data sheet is BMA280 ) which has capabilities of measuring temperature from -40 to 85 degrees celsius. It also specifies a Temperature Sensor Slope of 0.5K/LSB, where it fills up an 8-bit register. It's centered on 23 degress celsius when the register reads 0.

Obviously this is a signed number. one question I have is how does the slope play into this. If it really is 0.5K/LSB then it means per single bit I have increments of -272.65 celsius which doesn't make sense to me. What do they mean with the 0.5K/LSB slope?

If I take 125 (the overall temperature range) and divide that by 256 (8 bits) I get 0.488 which is about 0.5/LSB. What I don't understand is the 'K'. why is it a K and not a C.

This is in all the documentation and they are consistent except for a few locations, does K mean Celsius in some countries? This also spans into other datasheets as well. So I am beginning to suspect I don't know something I should.


texts:
Consider the circuit below:

It is known that:
\$V_{to}=2V\$, \$V_{DD}=5V\$, \$R_{D1}=1,0k\Omega\$, \$R_{D2}=0,6k\Omega\$.
\$K=0,4\frac{mA}{V}\$ for both transistors.
Determine the state of both transistors.

I have difficulty with this problem, because I don't know where to start.
Do any of you have some tips about how to start on a problem like this? And if so, what would you do for this problem?


texts: I have been asked this question: “Do you think the system will need deterministic time or real time responses?” The problem I have is distinguishing the difference between the two. I know that a real time response will respond to an input within a specific time period but I not sure what a deterministic response will do? Thanks.


texts: Determine the value of \$\text{C}\cdot\text{L}\$ in a LC circuit

texts:
When I have a series LC circuit, and I want that the switching-time (for the switch between the L and the C) is less then 10 microseconds, how can I determine the value of \$\text{C}\cdot\text{L}\$?

My solution:

$$\omega_\text{res}=2\pi\cdot\text{f}_\text{res}=2\pi\cdot\frac{1}{\text{T}_\text{res}}=\frac{1}{\sqrt{\text{C}\cdot\text{L}}}\space\Longleftrightarrow\space\text{T}_\text{res}=2\pi\cdot\sqrt{\text{C}\cdot\text{L}}\tag1$$

Now, it switches when:

$$\frac{\text{T}_\text{res}}{2}\tag2$$

So:

$$\text{T}=\frac{\text{T}_\text{res}}{2}=\frac{2\pi\cdot\sqrt{\text{C}\cdot\text{L}}}{2}=\pi\cdot\sqrt{\text{C}\cdot\text{L}}\space<10^{-5}\space\Longleftrightarrow\space0\le\text{C}\cdot\text{L}\le\frac{10^{-10}}{\pi^2}\tag3$$

Is this right?


texts: What are the plated holes on this PCB for?

texts:
In the top left corner of this snapshot, you can see a bonafide test point, TP12. Slightly down and to the right of TP12 you can see an exposed copper pad, also likely a test point.

What I am confused about are the numerous plated through-holes in this board (I am holding the board up to the light). They aren't connected to anything usually. Are  these likely to be used as test points, or engineered in "just in case" for future connections and test purposes?

Is this typically good practice? Generally I can see these holes go straight through the 4-layer board, and are plated top side and bottom side.   What could be the purpose of these, and is it a good practice to include them on a prototype circuit?  Also, I am guessing that the plated holes do not interact with ground and power planes.


texts: As part of a broader project, I am designing IC circuit using CMOS to one of the first steps I'm working on is the filtering a series of pulses with of the noise. The actual pulses are around 1 kHz so I am implementing 2nd order sallen-key high pass filter. Since the capacitance is limited to 1pF, the resistors in the circuit are instead replaced with a subthreshold transconductance amplifier (differential pair with a PMOS current mirror driving I1 & I2 - see attached picture). From my theoretical knowledge, Gm is driven by the bias current (Ib=I1+I2), which means I need around the 1 - 3 nA range ballpark and I'm not sure how to obtain these. How do I choose the specific bias voltage or transistor sizes to obtain the desired Ib? (as mentioned earlier, these are in subtrhreshold region i.e. vgs <= vthreshold). Any advice is greatly appreciated.


texts: Can I combine and re-split 2 coaxial cables for 2 signals in my home?

texts:
I have an existing coaxial cable running to my modem through the wall outside from my ISP. I bought an external digital antenna that I'd also like to run outside, but I don't want to drill a second hole and socket through the wall.

Can I use two splitters and temporarily run both signals through the same cable in the wall? So it would look like:

(outside) | (wall) | (inside)
ISP                     modem
---------           ---------
         > ------- <
---------           ---------
antenna                    TV


texts: What would be the band gap of a white LED?

texts:
So I was looking at the graph of the white LED, intensity vs wavelength and I observed two peaks.

Which peak would I choose in the formula Eg = 1240 / lambda?


texts:
I am attempting to make a circuit which triggers a 555 astable. The input is one of those IR beam break sensors with the output of the phototransistor going to a NOT gate and the output of that is connected to the gate of the thyristor through a 1k resistor. That thyristor is then powering the 555. The idea is that, when the beam is broken, the 555 will be triggered.

The only way that I can get it to work is by adding an LED in parallel with the 555, but it is quite unreliable. I think the problem is that the drain-source current is less than the holding and latching current, which are specified as 5 mA and 6 mA respectively. When I measured it, the current drawn by the 555 dropped as low as 3 mA, so this seems plausible.

Does anyone know of a "low current thyristor" or something else that would get this working reliably?

Any help is greatly appreciated.


texts: Best method of packet transmission between an array of sensor nodes?

texts:
Currently I'm working on a project where I'll have an array of four sensor nodes, each with three sensors. These sensor nodes need to send their data back to an ATMega controlled board for processing, display, etc. I had the idea of using some ATTiny85s, one on each sensor node, and use those to collect the data from the various sensors, then package it for transmission. I would like to have only one data wire, one ground wire, and one voltage wire connecting each node.

My question is this: what would be the best protocol for sending these packets of data over one wire? Each sensor node doesn't need to communicate with one another, and the ATMega only needs to accept input from the sensors, not send output too. I have heard of using the OneWire library with ATMega chips before but never on something like an ATTiny85. Or, would it be best to just try and send each packet of data "manually" (they're very small, no bigger than 100 bytes)?


texts:
I am using an LDR on an Arduino Pro Mini with an analog interrupt. The Arduino goes to deep sleep when there is no light or it's not busy:

Sleepy::powerDown();

The interrupt on the LDR looks like this:

PCintPort::attachInterrupt(lightPin, wakeUp, CHANGE); // lightpin = A0

This works great, not too fast. But the problem I'm having is that this only works with great increments in light, not with small increments. In fact, nothing happens when the LDR gives a little less resistance.

Is this due to the kind of sleep mode? Maybe because of some kind of insensitivity? Is there a hard-coded threshold?
I'm not that experienced with electronics or microprocessors. Am I missing something?

Waking up the Arduino when a small change in light occurs is critical for my application. I can't keep the Arduino constantly awake because it runs on a battery.

If you guys need anything more, like my full code, just say so! Thanks.


texts: Understanding differential ADCs and reference voltages

texts:
The Setup:

I am currently prototyping a wheatstone bridge setup to measure small resistance changes. I don't have the sensor I'll be using yet, so I've simulated it using trim pots. I am using a SAML21 xplained board. I have side A and B of the wheatstone's bridge connected to two of the SAM's internal OPAMPS with programmable gain. I then feed the OPAMP outputs into the 12 bit ADC in signed differential mode.

The Problem:

I have tried a few different configurations and I can't seem to make heads or tails of it. A bridge voltage of 2mV(or and imbalance of 100 ohms between R2 and Rx if you prefer) is created from a 1V source voltage. When referenced to ground as the OPAMPs do when it is passed through them, this is actually about 580mV for side A and 578mV for side B. The gain is set to 3, so when passed to the positive and negative ADC inputs it comes out to about 2.32V for the positive terminal and 2.31V for the negative.

What I get out is about -1000 ADC counts. This makes no sense to me. The positive end is set up to the node of higher potential. So I tried changing the reference voltage. It was set up to an internal 1V ref and I changed it to one labeled INTVCC0 with the comment "1/1.48VCC reference". The result then came out to 203 counts. Finally I tried another reference INTVCC1 commented "1/2VCC (only for internal VCC > 2.1V)". This resulted in about 700 counts.

To my understanding of the differential measurement, the reference voltage should not affect it since the difference between the two is all that matters.

I have tried changing the bridge voltage by a decent factor on all these references and the changes I see make no sense.

The Question(s):

Basically I am a bit lost as to what the ADC is telling me, and what changes I can make to get the desired measurement. I understand single ended well enough and what the reference voltage does there, but I cant seem to manage this transfer to differential. Can anyone point out problems or things to check?

Side question, could I take the line I'm using for the negative input and instead connect it to an external reference pin for the ADC and use the other input as the positive pin in the single ended input mode? If so, how is that different from what I'm currently doing?


texts: Temperature Sensor recommendation for measuring panel temperature

texts:
In my application, I am using a MAX6699 for monitoring the temperature of the PCB. The chip supports four channels, whereas I am using only 2 for monitoring the PCB temperature (through P-N diode). Now I have an additional requirement of monitoring the temperature of the metal enclosure of my system also. Since I have 2 spare channels in the above device, my first choice would be to use that to do the job.

However, the P-N diode which I used CMPT3906 is SMD and cannot be used on the chassis for monitoring. And I couldn't find any other component which is both chassis-mountable and can interface to my sensor through a cable or some discrete wires. Can anybody suggest me a solution?


texts: How can I reduce hum & pop from simple amp setup?

texts:
I am building a bluetooth speaker and am encountering two issues. Here is my setup so far:

When turned on, it gives two very loud POPS before working normally. Is there a simple way of delaying the audio for a few seconds when it is turned on? (other than adding a manual switch)
By themselves, each component sound great but when they share power, there is a lot of hum. I've researched and I think I need a "ground loop isolater". Where should this be placed within the circuit for maximum effectiveness?  (problem fixed by GLI)

Links: Amp Bluetooth Module


texts:
I'm sending data over Serial to a FRDM-kl25z via a printf statement on another uC;

    for (int i = 0; i <320; i++)
    {
        left--;
        right++;
        sprintf(left_arr, "%d", left);
        sprintf(right_arr, "%d", right);
        frdm.printf("%s,%s \n\r", left_arr, right_arr);
    }

And I receive the data with this code in a serial interrupt - called rx_data;

void rx_data()
{
    pc.printf("rx interrupted!\n\r");
    string current = "";
    while (rpi.readable())
    {
        current += rpi.getc();
    }

    PC.printf("%s", current);

}

I'm defining rpi as below;

Serial rpi(PTC4, PTC3);  // tx, rx

It only gets the first character, so the first byte, of the Serial transmission. I've tested with a counter too and the port is only readable for 1 loop iteration.

I've tested the code with other uC's - the LPC1768 - and it works fine.

It must be the fault of the Serial port on the FRDM I think, does it only have a 1 byte buffer or something?

Thanks!


texts:
What is the purpose of connecting capacitors to the gates in this bucket brigade device circuit? Why aren't they just connected to ground?
In every 2nd place there is a buffer transistor. How do these transistors prevent the voltage loss of the previous capacitors?


texts: How to Modify the Bidirectional Visitor Counter Circuit?

texts:
I have recently seen the circuit diagram of an interesting concept in the page - Bidirectional Visitor Counter using Microcontroller.

I am planning to do this project circuit on next week with few modifications. If we arrange this circuit to a particular large room for any meeting, it helps to count the people entering or leaving the room. But, here if the same person enters and leaves the room for more than once, it adds that many number of +1's to the total count. As a result, I think it is not possible to get exact total count of the different people that enter the room.

So, my requirement is that it should count only when a new person enters or leaves the room. i.e. if the person enters or leaves the room for more than once, it should identify it and treat it as only 1. As a result we may get correct number of different people entered or left the room. I think you understood about my requirement.

So, are there any other devices have to be added to this circuit? I have already asked my friends about this, but no one has given the solution. So, Can anybody kindly suggest me the required modifications to be done in this circuit?


texts:
Say I have a dark current plot (image mean over shutter time) with an offset (y-intercept) of 4100 and system gain K = 4.23, is the following calculation correct?

Variance of dark signal = sqrt(4100) = 64.

Temporal dark noise = sqrt(64)/K = 1.89 electrons.


texts: I'm working on my extension hat for Raspberry Pi 3. I would like to add a SWD/JTAG among all of the additional features. Have you ever dealt with this issue? How can I implement this? I mean, it's not meant to be a 6-pin header only. It's meant to be a whole hardware (microcontrollers, capacitors, resistors etc.). It should be ready to use by using a USB cable only. Can you recommend any ideas?


texts: What is being multipled to get rid of denominator in Node Voltage problem

texts:
I am trying to work through an example problem of using Node Voltage to find the voltage at Vx of a particular node in AC circuits using complex numbers. The example has the equation setup as:
$$\frac{V_{x}-V_{A}}{j40}+\frac{V_{x}-V_{D}}{44}+\frac{V_{x}}{-j166}=0$$
Solving this gives the following:
$$-V_{A}(-j40) + V_{x}(0.022+j126)-V_{D}(0.022)$$
Steps were skips and I am not sure what was multiplied to get rid of the denominator in the fractions. Since I'm dealing with complex numbers I thought I could just multiply the values in the denominator and then multiply that value to each of the fractions but I am not getting the same answer. Any assistance is greatly appreciated.


texts: Will I detect any signal if I apply laser light on one of the two light sensors placed in a sunlight?

texts:
I am trying to make a counter which should work in a solar light. I am thinking to use two ambient light sensors placed close to each other and use a differential amplifier. One sensor receives a RED laser light and sunlight on it. The Second sensor receives just sun-light. Therefore, I would have zero volts at the output if LASER is absent or else HIGH volts if it is present. Will this work?

EDIT:

I have two lasers with me. (1) Red laser. 660 nm and 130mW. (2) Green laser 532nm and 50mW.

I have this sensor: http://www.everlight.com/file/ProductFile/ALS-PDIC144-6C-L378.pdf  (also have 5mm too)


texts: What does the 'A' trailing letter in Atmel's ATtiny devices mean?

texts:
I have both on stock: ATtiny861A-SU and ATtiny861-20SU.

But I can not find out any difference between them except 'In-System Programmable via SPI Port' available for 'A' version.

Could anyone tell me what is the difference between those two devices?

Thanks!


texts:
I am struggling to find a solution for the project I am working on.

The circuit is powered directly from two 3V lithium batteries connected in parallel. The average power consumption of the circuit is around 10-20uA with some short current bursts up to 200mA. The circuit consists out few peripherals (BLE, MCU & etc.) and several indication LEDs. LEDs brightness should not vary significantly. System operational voltage is from 2.5V to 3.2V (estimation from the battery specs, components can handle up to 3.6V).

Questions:

Is there any way to protect batteries from cross charging without a significant increase in power consumption of the circuit? And without significant voltage drop?
The best simplest and cheapest way to drive the LEDs (10-20mA LEDs) with a forward voltage of around 1.9V to 2.1V. As when the battery is new the current will be higher and brightness will be higher and vice versa. So at 2.5V brightness will be significantly lower. Any kind of low power LED driver with the low quiescent current. Any suggestions?

Thank you in advance.


texts: Mic Amp Mixer and Audio Distribution, Won't Work! Help! (Update 2) (Solved!)

texts:
I'm new to this forum and I really don't know much about Audio Amplifier Circuits. Hope you can help me.

Here it goes:

So basically what I'm trying to do is a circuit that mix 3 channels, amplifies them and then distribute them into 3 channels.

The problem is that when I test the circuit in real life I can only hear sound when I blow in my mic, anything like shouting singing or talking won't do any sound.

As I don't know much about audio circuits, I would love some help to solve this problem.

I'm currently testing with this:

Headphone

Driver: 40mm
Frequency response: 20Hz-20KHz
Impedance: 32 Ohms
Sensitivity: 90dB SPL/mW

Microphone

Pickup pattern: Cardioid (Unidirectional)
Type: Pressure Gradient Electret Condenser
Frequency response: 50-20KHz
Sensitivity: -40dBV/Pa re: 0dB = 1 Pa, 1KHz
Test conditions: 3.0V, 2.2K Ohm

But I want to be able to use any headphone or any microphone.

So my questions are:

Is the circuit OK? Do I have to change something?
What may be the reasons for only hearing when I blow on the mic?
Any suggestions?

How i solve those problems

The circuit is OK, i had to change the value of all the POTs from 50k to 5k, also all the polarized CAPs to non-polarized and reduce them from 47uF to 1uF all but the ones from the input, i change those for 10nF.

If you need any other info just tell me to add it.

Update:

Now, In Proteus I'm losing the signal after the 5k POT. Whats happening?

A Signal is after the POT, while B is Before the POT.

Solved: the problem was Proteus it was bugged.

Update 2

Well now the circuit looks like this with most of the problems solved.

It works but now i have another problem, there is some background noise.

More Questions:

I'm testing the circuit in a Protoboard, moving it to a PCB changes anything?
Is there something i should add or change to reduce this background noise?
PS: when the mic is not connected or muted the background noise stops.

Solved

Had to take away resistor 24 from the 2nd update circuit.


texts: PC Fan PWM signal circuit using 555 timers: Can anyone explain this circuit to me?

texts:
I'm looking at building a 4-wire PC fan PWM circuit. The goal of such a circuit is to send a PWM control signal to a 4 wire PC fan, so that the fan can modulate it's speed (NOT to pulse the 12V supply).

One circut for this that is widely cited is the 556 based circuit located far down on this page. The circuit looks like this:

I can't for the life of me see how this circuit can work. My understanding of the goal such a circuit is (per the specs here) to produce a stream of pulses at 25kHz, and to vary the width of each of those pulses.

This circuit has the pot tied into Trig1, so as far as I can tell it'll vary both the width of the pulses as well as the frequency of the pulses? Or do I just not understand it (won't be a shock).

I would have assumed that one should build an astable 555 triggering at 25kHz, and then feed that into a monostable 555 that varies the pulse width?

Side note: If this circuit isn't the best approach for a fan PWM, can anyone recommend a better one?


texts:
I have a PCB so dense, there's nowhere to put a few of the last caps, which have to be under the fpga.

The 0201s can bridge 2 vias, placed on a power and ground the fpga needs.

If I were using 0402s, I'd just put them right there.  With those vias smack dab in the middle.

But the 0201s only reach halfway across the vias on both sides.

If if I put them there, the thermal behavior ought to be fairly similar, so perhaps not a source of tomb stoning.

But the pads would be formed from mask, with the other half of the via extending out.

Can I get away with it?


texts:
What is the best way to make a 50 volts regulated power supply? I was thinking to incorporate the LM78xx IC only to find out the maximum voltage they support is around 24 V and 1 amperes. Another possible solution is to stack/cascade Zener diodes until the equivalent voltage is around 50 V. What solution is the best and reliable, assuming we can consider cost and performance also.

PS: I will use the regulator to audio power amplifier which will draw around 1-3 A.

Input: AC 220 volts 60 Hz
Output: Pre amplifier and Power Amplifier (Audio)
ripple - 5% tolerance


texts: I'm trying to build a msd with stm32f4 which will be connected to a pc with USB. I need to visualize it as "USB drive" formatted in FAT. Initially I was planning to use a nand flash but I can't use it "bare bone", I need a translation layer, can someone please link application notes/articles about it? now that i know what I need I will also search myself!


texts: Ethernet connection using only one twisted pair

texts:
For my degree work, i make some reseaches for different bus systems and
i've found ethernet a bit different than others: The old 10Base5 and 10Base2 ethernet used only one pair of conductor to communicate the nodes with each other (coaxial cable) and implemented CSMA/CD to avoid/manage transamission collisions. Thats fine. However modern twisted pair ethernet equipments more likely connected as point to point devices with full-duplex capability, where there's no collision, but still implements CSMA/CD.

It is possible to create an ethernet bus line using only one twisted pair?
Or this one conductor line connection is possible only for the old coaxial ethernet?


texts:
Signal is something that carries information. Usually, something is a pattern of variations of physical quantity that can be manipulated, stored, or transmitted by a physical processes.
I am wondering that how image can be a signal. Ok, it is stored, manipulated, transmitted digitally, but how it can carry variations?
Also how video can be kind of a signal?


texts: How Exactly Current Flow Through a Capacitor?

texts: Capacitors behaving as an open circuits, How can we understand the concept of the Electrons flowing through a capacitors.


texts:
I’m using the LM7321MAX operational amplifier to supply a 12V digital signal from a 5V source. For the op-amp supply voltage: is it better to use something close/equal to my output value (like 12V) or further away (like 22V)? I know the internals of an op amp are mostly BJTs so am wondering if I’ll draw the same supply current in either case, with the 20V variant therefore using more power. Thinking the 20V->12V will happen across those BJTs
Thanks for your help!


texts:
I want to draw the bode plot of a tranfer function:

$$
H(j\omega)=\frac{100j\omega T}{j\omega T + 10}, T=1s
$$

Now I have

$$
H(j\omega)=\frac{100}{1 + \frac{10}{j\omega T}}, T=1s
$$

Using a double log scale:

$$
20*\log{H(j\omega)}=20*\log{\frac{100}{1 + \frac{10}{j\omega T}}}, T=1s
$$

And can I just insert omega and compute the points for the plot?

Like for omega = 1000

$$
20*\log{\left(\frac{100}{1 + \frac{10}{2*\pi*1000}}\right)}=40-20*\log{\left(1 + \frac{10}{2*\pi*1000}\right)}=39.9...
$$

Is that correct?


texts: Why is usage of a current source preferable over a voltage source for charging capacitor?

texts:
I came upon this sentence in a paper concerned with dielectric elastomer actuators (DEA):

  Due to the capacitive behavior of a DE, a converter with current source functionality should, therefore, preferably be used to adjust the voltage vp, and by this the electrostatic pressure, in (1).

Why is a current source preferable compared to a voltage source?


texts: High Pass filter gain at higher frequency than cutoff frequency

texts:
As i know , it's very common easy to  find cutoff frequency and calculate gain at highpass filter.

This is my circuit;

simulate this circuit – Schematic created using CircuitLab

My source is 1mVp,300Hz frequency and high pass filter cutoff frequency is 10.26 Hz if i wasnt calculate wrong.

What is the problem ?

When i apply this signal to HP filter. Output is 965.67139µV from LTSpice , 988µV from ADsimPE but from my calculation output has to 0.9999 like that.

My Calculation:

\$ X_c = \large{\frac{1}{2*\pi*300*4.7\mu}} = 112.875\Omega \$

\$ Z = \sqrt{X_c^2 + R^2} = 3301.92\Omega \$

final voltage divider is

\$ V_o =  \large{\frac{1mV * 3300}{3301.92} = 0.9994mV} \$

it isnt equal some much is it ? I mean if from the spice programs output is 0.9999 or 0.9998 or maybe 0.98 i can say there is error or maybe Negligible case which i dont know but they are saying 0.96 or 0.988... I cant expect that

There two possible in this situtation:

My calculation is wrong or SPICE programs are wrong.

and i also check it AC Analysis in two SPICE programs. they are say gain = 1 at 300 Hz .

Someone explain me , what's going here??? i cant even a trust simulation programs ?

Transient Response

ADIspicePE,

LTSpice,

AC Analysis,

ADISimPE,

LTSpice,


texts: Why does FreeRTOS API function xEventGroupSetBitsFromISR cause error when I use it in an ISR?

texts:
I am using FreeRTOS on MSP430 microcontroller and I have an error that occurs when I use API function xEventGroupSetBitsFromISR() inside of ADC interrupt routine.
I have searched online and I saw that I need to go to FreeRTOSconfig.h to set certain flags to 1 so that this API function could work but I don't have these flags in my header file. Could I just add these flags my self?
Here is text that says which flags to set:

INCLUDE_xEventGroupSetBitFromISR, configUSE_TIMERS and INCLUDE_xTimerPendFunctionCall must all be set to 1 in FreeRTOSConfig.h for the xEventGroupSetBitsFromISR() function to be available.


texts: Need help designing and implementing an op-amp based distortion circuit

texts:
I've been attempting to design a distortion pedal for use with my bass guitar and amplifier. The simulations in LTspice were promising, I moved to implement it and, in short, it did not work.

Note: The amplifier used in the circuit is merely illustrative. I am actually using an OPA2134. The sheet is here: https://www.ti.com/lit/ds/symlink/opa2134.pdf

This is the basic circuit, a bipolar power supply to power the op-amp and provide a 0V reference, the bass below it, with its impedance accounted for, the amplifier to its right, with soft clipping on top and hard clipping on the right. The bass amplifier is represented by the 1M input resistance.

From what I know, soft clipping is basically logarithmic amplification (high voltages become not so high) with a capacitor in parallel to lower the slew rate. Hard clipping is just cutting the wave once it goes above 0.7V or so (depending on the diode of course).

Now, this works fine as is (simulation-wise), and here are two examples of soft and hard clipping, respectively:

Note: Green is the output, red is the input scaled by 10. The original signal should have an amplitude of around 40mV, I believe. Also, for hard clipping to happen the soft clipping part of the circuit must be disconnected. This would be done with a switch in practice.

Seeing this, I build a little test circuit, with only the bipolar supply and the amplifier. First I used a 220 Ohm input resistance and a 440 Ohm for feedback (so the signal would be amplified by a factor of 3). It worked, but the noise when I played low frequency notes was noticeable.

After that, I switched the feedback resistor for a 10k potentiometer (wired up as a variable resistor). The amplifier produced a very loud, low frequency noise at all times. The bass was (just barely) audible, but it sounded very quiet considering the ~50x amplification factor.

So far, my questions are:

Is the bipolar power supply adequate? Would input biasing be better in this situation? If so, why?
Is the value of the input and feedback resistors adequate? Should they both be higher/lower?

I thought filtering the input signal might help, so I moved to design a pair of simple filters with the components I had available. This, however, distorted the signal massively. Here are the filters:

I must've done something really dumb (filters are supposed to be quite simple) because the signal looks like this:

As you see, the input signal now has a DC offset, and the output looks like that.

Here's another pair of questions:

Are the filters correctly designed?
Is there some sort of incompatibility with the bipolar supply?

I hope I was clear enough with the questions and examples, if you need any extra information let me know. Thank you in advance for your time!

SOLUTION

As described in the answer, the solution was using a voltage follower in the power supply to provide a much more stable ground node. The new power supply is below:

Note: The wires that intersect but don't have the blue square are not actually connected, so if you have the same issue, don't connect your output to the op-amps power supply :)


texts:
the question and solution is given below:

How did he know that 10 kVA is transformed by magnetic induction?
SOURCE: Electrical Machines, Drives, and Power Systems
by Theodore Wildi. Sixth edition, 2014.
ISBN 10: 1-292-02458-5
ISBN 13: 978-1-292-02458-5
Pearson Education Limited


texts:
This is a follow up question to this question.

I have attempted to draw a schematics of my setup for the 7489 below. Without the switch closed, the LED D1 is on. Then the switch is closed, then also LED D5 comes on. If I connect the ME to high, then this behavior does not change.  Also, if say D2 is brought high with the other inputs low, then all the LEDs are off.

Does this mean that I am doing something wrong, or have I broken the chip?

(I have also tried inserting pull up resistors (1kOhm to 4.7 kOhm) on the address inputs.)

simulate this circuit – Schematic created using CircuitLab


texts: Selecting true crystal settings for 328P [7.3728 MHz]

texts:
I want to make a new board working with 115200 (gsm modem) UART. so I want minimum baud error rate. I look at

https://cache.amobbs.com/bbs_upload782111/files_22/ourdev_508497.html

table and decide to work with ATmega328P 7.3728 Mhz / 3v3

The second step is choosing the right XTAL capacitance (Ce)

Cl = 18 pF (Load Capacitance of External Crystal) [ECS-073-18-20BM-JEN-TR]
Cs = 5 pF (Stray Capacitance; in additional sources says you can take it 2-5 pF)
Ci = 18 pF (ATmega328P datasheet; XTAL/TSOC capacitance)

This formula is given in ATmega datasheet

  Ce = 2Cl - Cs - Ci

so

Ce = 2.18 - 5 - 18

External Capacitance is

Ce = 13 pF
CRYSTAL ESR = 70 ohm

is that a true calculation? and true settings for my clock setting?

Fuse Settings :

 Low Byte Fuse : 0xFD
 High Byte Fuse : 0xDA
 Extended Byte Fuse : 0xFD


texts: Best way to power my 3.3V circuit from a battery with ultra low current requirements

texts:
I have an application featuring the ESP8266 and I am trying to figure out the best but more important right way to power it. The ESP is the only main load in my application, its current draw will range from 20uA in deep sleep mode up to around 150mA when the RF calibration takes place.
I am planning to use either a LiPo or LiIon battery so the voltage of one of those cells will range from like 4.2V down to 3.0V. It is really important that the draw does not exceed the 20uA by much when the ESP is sleeping, since the circuit is supposed to be running for about a year on one charge.
I tried LDOs like for example the MCP1812 rated for 3.3V fixed output and it actually worked. But I think I used the device outside of its operation range as soon as the battery voltage was 3.3V as well. I am not sure about switching supplies or LiPo charge controllers, are there any that have built in regulation and are super efficient? I think I need a charge controller anyways to provide necessary protection to the batteries. Anyway, this is a field I am not familiar with and I am curios what are the possibilities here.


texts: what is the difference between voltage output swing at no load vs at 10k load?

texts:
referring to page 6 of this op amp reference sheet under the heading "OUTPUT" http://www.ti.com/lit/ds/symlink/opa188.pdf

there are two output voltages - one for no load condition and one for 10k load condition. could someone provide me a circuit schematic so I can see where this load resistance is located? I'm new to designing op-amp circuits


texts: Syntax error selecting a range from a range

texts:
I'm trying to run an old Bitcoin miner project in Vivado. The old code is written in Verilog and the rest of my project is in System Verilog.

I have a syntax error I don't know how to solve. It basically boggles down to a single line (that you can see in the full source code here)

data15_p1 <= `S1( S[i-1].data[`IDX(15)] );

Expanding the macro manually and cleaning it up to replicate the error, I get:

data15_pl <= ( { S[i-1].data[511:480][16:7] } );

Here is what I understand is happening: the IDX macro takes a 32 bit subset from the 512 bits s[].data. [16:7] is then used to try and take bits 16 to 7 of those 32, but Vivado complains with the "Range is not allowed in a prefix" error.

Do I need to rewrite the code using a temporary wire variables to get this to work?

Edit: I think not because I can't use a wire in that scope? Using a register would add delays. Maybe the only option is manually expanding and changing all of the defines?


texts: Good design for a basic non-IC class D audio amp?

texts:
I'm looking for an existing design for a good yet simple class D audio amplifier using discrete semiconductors, no ICs.  The purpose is educational, with a final product that actually could be used.

not bad quality (but we don't need top quality, or to compete w audiophile gear)
enough power to drive modest size speakers (it's hard to be quantitative about this)
no exotic parts.
within reach of serious hobbyists, EE students
not too simple; not for beginners or kids to make.
need not be commercially viable or survive outside an electronics hacker's home.
small transistor count prefered, but no need shave every penny or cut corners.
illustrates nicely the operation of class D amplifiers


texts: Change serial converter voltage from 5 V to 3.3 V using resistor

texts: I have a USD-TTL converter which uses 5 V. Can I change the output voltage from 5 V to 3.3 V using a resistor? Product: https://www.amazon.com/Breakout-USB-TTL-Module-Lilypad-ATmega328/dp/B01LQYO1AI/ref=mp_s_a_1_2?ie=UTF8&qid=1543742183&sr=8-2&pi=AC_SX236_SY340_QL65&keywords=lilypad+arduino+usb&dpPl=1&dpID=41-vghnWhkL&ref=plSrch


texts:
I have designed a clamping circuit to protect pins of my microcontroller and I have to add a low pass RC circuit at the microcontroller end to filter out the high frequency noise. My circuit analysis is weak and I am not sure what part R1 and R21 would play in determining the frequency.

Resistor R1 is used to bias the diodes in a region where their forward voltage is 0.2.
So the node between R1 and R2 is maintained at 3.5 Volts.
R21 is a pull down resistor because the input voltage is 12-20V or open circuit.


texts: Physical interpretation of Re(Z) = max(Re(Z)) and Im(Z) = 0

texts:
I have plotted the real and imaginary parts of a device's input impedance with a VNA.

What would be the best physical/electrical interpretation of the real part peak along with the imaginary part zero ? I fail to give a proper explanation, even though I know something is happening.


texts:
I have created a system using arduino where it controls 5 different electric lines. For example:
Line 1, Line 2, Line 3, Line 4 and Line 5. What arduino does is, it turns on the Line 1 if it has power and if it doesn't have power it turns on the Line 2 and etc. Arduino turns on/off the 5V relay and it has at least 5 sec interval when switching from one line to another(in this case I have 5 x 5V relays). It is working perfect and I am very happy with the system, however I am concerned about relay fails to disconnect when commanded.

For example: If Line 2 was on and suddenly Line 1 also gets power and arduino will turn off Line 2 and after 5 secs it turns on Line 1. What if Line 2 relay didn't brake the curcuit? I think I will have a fire or something really bad.

My question is, can I some how make fuse so that never more than one lines will be connected?

See my schema:
The reason I am doing this is, in our office we have 5 different lines of electric and I want to control it automatically. Also I would like to see which line has power and being able to control it from the computer.


texts:
I've been studying TE and TM modes on waveguides for microwave frequencies.

It basically consists on applying Maxwell equations on a rectangular metallic cavity, with infinite length on \$z\$ direction, and finite on \$x \$ and \$y \$ directions ( say, length \$a\$ on \$x\$ and \$b\$ on \$y\$).

On TM modes, we admit \$ H_z \$  =0, and apply boundary conditions \$E_z \$= 0 on \$x= 0,x=a,y=0,y=b\$ ( since its a conductor )

On TE modes,we admit \$ E_z \$=0, and apply boundary conditions \$ \displaystyle\frac{\partial H_z}{\partial y} = 0 \$ on \$ y=0,y=b\$ and \$ \displaystyle\frac{\partial H_z}{\partial x} = 0 \$ on \$x=0,x=a \$.

My question is: why TE boundary conditions involve derivatives of \$H_z \$ equal to zero, and not \$H_z\$ itself null?

All of these calculations can be found on Sadiku's Electromagnetism ,page 496 if 3rd edition.


texts: I2C communication with AVR - how to let the lines "float"?

texts:
I am trying to implement I2C using an AVR controller without the designated internal TWI registers.

The I2C protocol requires that the Master device drives the SDA and SCL lines to begin with in order to address and begin a communication transaction. The problem I am having is that after an address is sent over the serial line, you must let the data line "float" (that is, be pulled high by the pull-up resistor) in order for the slave to drive the line low for an ACK signal.

I am able to successfully successfully address the I2C device, but when I attempt to let the line "float" I am having a bit of trouble. I was under the impression that in a input HIGH-Z state (tri-state that is - DDRX 0, PORTX 1 for a particular pin) would essentially be modeled like:

However, the state of the SDA line remains high even though the I2C device is responding with an ACK bit by driving the line low. I know this to be true because I set a sizable delay after setting the pin as input. During this delay, the line remains high. However, if I remove the wire tying the MCU to the SDA line then it will drop to LOW due to the slave device.

In short, how do you handle "letting go" of a line to ensure its potential is driven by the devices on your I2C data line rather than being influenced by the MCU?

/* Pin and direction register manipulations */
#define I2C_CLKDEL              10 //10uS
#define I2C_PORT                PORTB
#define SDA                     PB0
#define SCL                     PB1
#define set_high(port, pin)     (port    |=  (1<<pin))
#define set_low(port, pin)      (port    &=  ~(1<<pin))
#define set_in(portDDR, pin)    (portDDR &=  ~(1<<pin))
#define set_out(portDDR, pin)   (portDDR |=  (1<<pin))

void clkStrobe(void){
    set_high(I2C_PORT, SCL);
    _delay_us(I2C_CLKDEL);
    set_low(I2C_PORT, SCL);
    _delay_us(I2C_CLKDEL);
}

uint8_t sendByte(uint8_t byte){ //MSB first
    uint8_t count = 8, ack;
    set_low(PORTB, SCL);

    while( count-- ){
        if( byte & 0x80 )
            set_high(PORTB, SDA);
        else
            set_low(PORTB, SDA);
        byte <<= 1;
        _delay_ms(I2C_CLKDEL);
        clkStrobe();
    }
    //set as input and read in the I2C port data
    set_in(I2C_PORT, SDA);
        _delay_ms(1000);
    ack = PINB;
    set_out(I2C_PORT, SDA);
    clkStrobe();    //clock in the ACK bit

    return (ack & (1<<SDA)); //return ACK bit
}

A large delay was inserted after SDA on the MCU is set as input for testing. The line remains high. If the SDA line is removed from the MCU (wire no longer connected), the SDA line is driven low by the I2C device being addressed (device is sending ACK). Clearly I am doing something wrong here.


texts: What is the smallest voltage that an Arduino UNO can read from the analogRead()?

texts: Is there a source that I can find for the kind of Arduino.


texts: Can I use a single wire as the BT Antenna?

texts: I am using the following BT Module and was wondering if I could just use a single wire as the antenna? I have seen wifi devices with a single wire soldered or connected to the board with a short run of the wire being used as the antenna.


texts:
I am working on a circuit to drive some water pumps. I intend to achieve a double galvanic isolation between the pumps and the CPU to ensure nothing bad will happen to the CPU.

Here is my schematic:

I am using a 4N35 optocoupler to achieve the first stage galvanic isolation between the 5V control signal and the relay driver circuit.

The relay driver circuit consists of a BC337 NPN BJT(Q1) a flyback diode (D1) and a resistor to the base of Q1 (R2).

As Q2 is intended to be used in saturation mode, I learned that Ic = VCC/RC, in this case VCC is the relay supply which is 5V and the coil resistance is 70Ω with 10% error, hence the worst case resistance should be 63Ω, knowing this Ic = 5/63 = 79.3mA.

Knowing Ic is now posible to solve for Ib, Ib = Ic/Beta, I am using the lowest HFE found on the BC337 datasheet, this value is 60.

Hence Ib >= 1.32 mA.

So now I know that I need at least 1.32 mA feeding through the base of Q1 for it to be properly saturated. The thing is that I don't know if R2 is needed on this circuit, because the optocoupler is already sourcing current.

If R2 is needed, how can I solve for its proper value?


texts:
I have found an article that suggests using one, two or three capacitors to filter DC motor noise.

over the motor terminals
from each terminal to the casing
both between terminals and between terminals and casing

Why is it better to add capacitors between motor terminals and a casing as opposed to putting all three of them across the terminals?
Does the metal case somehow contain the EMF when connected to the terminals?


texts: When a datasheet specifies output current is it per pin or aggregated for all pins?

texts:
When a datasheet specifies something like output current, as with the 74FCT244 or  for example, is this referring to the aggregated output current between all pins or the capacity of a single pin ?

74FCT244

Other device example

Also, it specifies above for the 74FCT244 that with an output HIGH, the max current is -15mA, while with output LOW the associated current shall be no more than 64mA. Clearly one of these refers to the capacity of the device to source and sink current, but the relationship between current sign and output voltage appears backwards to me. Namely, the datasheet says with a HIGH output then it appears to allude to sinking 15mA (indicated by the negative sign). Similarly, the LOW output voltage has a capacity of 64mA .. sourcing? (positive sign).


texts: Create a unique file name inside an entity instantiated multiple times

texts:
I have a design instantiating a component many times in different situations. I want to trace some internal behaviours it has using text file output.
Here is a snippet example I use in a component instantiated only one time and it does what I want.

        rdprint : process(axi_clk)
        variable line_out : line;
        file adc_file     : text open write_mode is "simresult\DMAbufferrd.txt";
    begin
        if (rising_edge(axi_clk)) then
            if dmaBufRen then
                write(line_out, dmaRDptr); -- write buffer address, when 0 means it's a new packet
                write(line_out, string'(","));
                write(line_out, to_hstring(dmaBuffer(dmaRDptr))); -- write data in hex format
                write(line_out, string'(","));
                write(line_out, signed(dmaBuffer(dmaRDptr)(23 downto 0))); -- extract payload in integer format.
                writeline(adc_file, line_out);
            end if;
        end if;
    end process;

The problem happens when trying to trace inside a component that is instantiated multiple times. Using this method will have all instances try to open the same file. It needs a unique trace file name for each instance. Does anyone know how to do that. It needs to be a unique name that can be file system compatible (no special character like :: etc). I'mprobably looking for some king of attribute that can give me the current instance name
like:

file adc_file     : text open write_mode is "simresult\"& this_instance & "DMAbufferrd.txt";


texts: Adding one to a value in C++ for a PIC Micro

texts:
I have a PIC 12f629 and I am going to program it. I have a value for the output:

GPIO = 0b000000;

and am using it in a loop that iterates 10 times:

for (i = 0; i < 10; i++)

My problem is that I need to increment GPIO to be able to address different memory regions.

How could I do that in C++?


texts: Can I use this DPDT relay with this circuit? If so, which wires connect to what terminals?

texts:
I'm following this tutorial to wire an automatic chicken coop door. The DPDT relay they're using is different to my relay so I'm finding it difficult to understand which wires connect to where. I'm completely new to all things electronics, could somebody help me please?

Here's the wiring diagram for my relay:

Here's the full wiring diagram on the tutorial:

The sensor I'm using is also different to the tutorial, this is: https://www.amazon.co.uk/gp/product/B00BU78GX0]

This question is different from my previous question because I'm asking about the differences between the relay used and the one I have. I'm not asking about splicing wires, which got an answer which I marked as the correct one. Thanks.


texts: Simulate and Plot each Vout given 40 Resistances and a 4 Resistor Network


texts: Why the current flowing through an induction heater increases when something is heated up?

texts: I think the whole question lies on the title. I can't understand how the material put inside the coil affects the total current drawn.


texts:
So my senior project is due Thursday and because of my extreme wits and knowledge I accidentally connected A 7912 Voltage regulator the incorrect way because I was unwary of the different pin-out.  I went to radio shack and they did not have any 7912 regulators. Is there any common household objects that have a 7912 or equivalent that someone may know about? I understand this is a long shot but I really need this part my project will not work without it. Thanks

EDIT
Here is a Picture of the schematic, The Negative 12 volts are used for a reference for a LT6105.


texts:
Consider the following simple buck converter

It consists of an NMOS input device, a diode, inductor and capacitor and a load.
If we are limited to a gate voltage on the NMOS device of 12 volts peak-to-peak, what is the maximum input voltage that we would be able to use with this limitation? Assume a threshold voltage of 3V.Neglect NMOS on-resistance

Here's what I think:

For an NMOS
$$V_{GS} >V_{TH}$$
$$V_G - V_S > V_{TH}$$
Neglecting the NMOS on-resistance, we get:
$$V_G - V_{in} > V_{TH}$$

Since we have a 12V-p-p signal at the gate, the maximum gate voltage is 6V. Substiuiting this, along with our 3V threshold voltage, I get
$$6V-V_{in} > 3V$$
$$-V_{in} > -3V$$
$$V_{in} < 3V$$

Is this correct?


texts:
So for a school project where we have to make a lesson plan for kids to learn stuff out of "lame" experiments, I was assigned potato clock. I could not for the life of me find a simple 1.5 volt led clock, and I was not allowed to purchase something that is a kit or part of a kit. I ended up purchasing a simple rotary clock, instead.

The potato battery I rigged up puts out 1.60-1.80 volts so says my multimeter, but when I alligator clip it to the clock, nothing. I pulled a double a battery from a controller, and it works, but not the potato batterie (also tested the battery with the multimeter to see if the multimeter is broken, it came up right around 1.5 as well). Why will my potato battery not power the clock?


texts:
I'm building a wearable Bluetooth device. When a button is pressed on the device, it sends a signal to the user's smartphone and consequently an app on said phone. I'm an app developer with no engineering background - but I've been doing plenty of research.

A means of communicating a button press into a message sent to the phone is necessary. I'm told making this from scratch will cost about $30,000 to have a competent engineer design it. I'm trying to find ready made solutions, but am struggling to find a Bluetooth module with an analog input built in which is what I believe I need.

Is there a ready made solution for what I'm doing or some method, tutorial or kit available that I'm overlooking? It seems crazy to me that there isn't, but my research has been fruitless thus far.


texts: Why cable delay is limited to 26ns in USB 2.0?

texts:
The usb.org FAQ explains this limitation this way:

  The cable length was limited by a cable delay spec of 26ns to allow for reflections to settle at the transmitter before the next bit was sent. Since USB uses source termination and voltage-mode drivers, this has to be the case, otherwise reflections can pile up and blow the driver.

But this explanation is clearly not valid for USB 2.0. Hi-Speed mode operates on 480 Mbit/s and it's single bit transmission time is only 2ns. In 5 meter long cable reflections would not settle at the transmitter before the next bit is sent in Hi-Speed mode.

26ns is about 38 MHz, so it is not very clear why was it introduced for 12 MHz Full-speed USB 1.0 mode too. But ok... raise time + delay + fall time, the choice may have sense, at least.

It is not an ACK delay time. Device response time was set to ~ 400ns by USB specification. It can't also be lower than 50ns for 5 meter long cables.

Where does this mysterious constant of 26ns came from and how is it relevant to the Hi-speed USB 2.0?


texts:
I'm a programmer, not a wizard.  I've read up as much as I can, including the similar questions list from this question, but, they blew by me pretty quick.  So here we go:
A project I'm doing some code for started on Arduino, at 5V.  It has a flow meter (Hall effect sensor) at 5V, a pressure transducer sensor at 5V, and a I2C LCD display at 5V.
Now the board is being changed from Arduino, to a 32bit board that will run at 3V3, and has zero 5V tolerant pins.
Here are my questions:

The LCD at 5V is only getting input over I2C, but I worry that the 1s may be weak, so I'm going to add a bi-directional level-shift between the board and the display.  Good idea?  Unnecessary?  Alternative ideas?

The flow meter (Hall effect sensor), powered by 5V, sending input back to the controller... will it exceed the max threshold for 3.3V?  I would think so, as I would think the pulse back is 5V HIGH.  Can I use the same bi-directional level-shift as #1, as it has 4 channels? I would think so, as it is just coming back HIGH, in pulses.

The pressure transducer sensor is analog, so obviously it is coming back at 5V.  Can I use, yet again, the same bi-directional level-shift between the input and the board, or is there a better way?

I figure if I have to add a component(s), I might as well add the fewest possible, to limit the number of components that can fail.  So if I can get away with a single 4 or 8 channel level shift... I'm happy.
Thanks!
I'd add in spec sheets for all the items, but they were just stuff bought randomly off Amazon, I'll do the best I can to give as much as I can find on them, since I don't know their internal components.
The flow meter is a -201 variant, YF-S201 is about the closest I've seen to having data on it.
The pressure transducer is linear, so, from description:  0-500 psi (Gauge Pressure) Output: 0.5-4.5V linear voltage output. 0 psi outputs 0.5V, 250 psi outputs 2.5V, and
500 psi outputs 4.5V
The LCD is a 204A variant. 20 characters, 4 rows


texts: Why is there no rolling shutter when using a mechanical shutter?

texts:
So I know it might not be the best place to ask this question, but maybe some of you are familiar with the mechanics of digital mirrorless cameras and the technology of CMOS sensors.

I don't quite understand why electronic image sensors, that create rolling shutter artifacts, don't produce images with this issue, when combined with a mechanical shutter. The thing I don't get is the following:

Rolling shutter happens due to the sensor readout from one side to another (usually top to bottom), so the actual image is stitched together from scan lines of different consecutive moments. In my understanding the scan line readout mimics the mechanical shutter window traveling above the sensor(?). Now when a mechanical shutter is used in front of the sensor, the shutter takes over this task, whereas the sensor is read out globally at one time(?). Therefore rolling shutter artifacts are not appearing in the final image. BUT if the sensor can be read out globally at one time, why is this not simply happening, when using a electronic shutter? Why can the sensor not just be turned on and off within e.g. 1/2000 of a second completely, avoiding rolling shutter? Why is the "scan line method" needed to take an image, if the sensor can be turned on and off globally?

When I have a camera, that can take still images at 10fps with a mechanical shutter, why doesn't it mean the sensor can take images at 10fps electronically without producing rolling shutter?

I've found this post which explains the general reason for rolling shutter, but not the specific question I have.

I don't even know if my assumptions are correct, but I'd be pleased, if someone could shed some light on this.


texts: Is it possible to replicate the Thomas Henry X-4046 circuit using the PLL_Virtual component in Multisim?

texts:
The part of the circuit I'm having trouble implementing is the transistor pair that are used to control the output frequency (going into pin 11 of the 4046).

I have removed the Exp FM, Linear FM, hard sync, 1V/Oct and sine and pulse outputs as I am just interested in creating a triangle, rampoid or sawtooth output with an adjustable frequency. My circuit currently looks like so:

However, I am confused about where the output of Q2 should actually be connected. According to the schematic, it should be connected to pin 11, however, the CD4046B data sheet shows that pin 11 is connected to the VCO:

I've tried connecting it to both the LPF output and the VCO output (which is fed back into the phase detector input), but neither of these seem to have any effect on frequency.

I'm not sure if there are other problems with my circuit too, although I've followed the schematic pretty much exactly. If there are I would appreciate them being pointed out, as this is my first time building a synth.

edit: the circuit for the outputs of pins 4, 6 and 7 can be found here: http://www.birthofasynth.com/Thomas_Henry/Pages/X-4046.html#X-4046_VCO_Schematics


texts: Protocol to be used to make microcontroller to work as mouse

texts:
I'am Doing a "Wireless mouse using data glove" . In this user wears a Hand glove equipped with sensors, microcontroller & transmitter. I could detect left & right movement of hand & i could detect clicks & transmit them using transmitter.

The receiving module consists of a receiver, microcontroller and receiver should be connected to USB of computer. Now, Which protocol i should use to indicate the computer to move mouse pointer accordingly ?


texts: Why does the resistance change when additional resistors are added here?

texts:
Please excuse what is probably a very simple question. I don't know the correct terminology to describe this better than "added here" as these don't appear to be "in parallel" or "in series" since they're floating off to the side.

Here I am measuring a 100K resistor and it shows as ~100K on the multimeter.

But when I connect the resistors up like this then the resistance changes. I haven't moved my multimeter test points.

I've drawn these out and simulated them using Circuit Wizard.


texts: Height adjustment of PCBs in increments of 0.05 mm

texts:
I have a 1.55 mm thick FR4 PCB with a thru-hole sensor on it. I was told these 1.55 mm are more of a suggestion than a number you can rely on. In fact the tolerances of FR4 PCBs are around 10 percent. This means that a 1.55 mm thick FR4 PCB can have around 0.1 mm of thickness variation across production batches. In my case there is a thru-hole sensor on this 1.55 mm thick PCB and the 0.1 mm of thickness variation has caused issues (the PCB is currently mounted on a piece of ABS plastic with four screws).
I cannot solve this issue by adjusting the sensor and thus adjusting the height of the PCB is my only option. I have looked into board spacers and standoffs as a way to negate this 0.1 mm in thickness variation, but could not find anything small enough. I have also thought of using thin plastic washers or shims in combination with small screws, but this seems like a crude method.
Are there sophisticated methods to height-adjust PCBs in steps as fine as 0.05 mm?